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},
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"description": "for...of",
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"spec_url": "https://tc39.github.io/ecma262/#sec-for-in-and-for-of-statements",
"support": {
"chrome": {
"version_added": "38"
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"chrome_android": {
"version_added": true
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"edge": {
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"edge_mobile": {
"version_added": "12"
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"version_added": "13",
"notes": "Prior to Firefox 51, using the for...of loop construct with the const keyword threw a SyntaxError (\"missing = in const declaration\")."
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"version_added": "14",
"notes": "Prior to Firefox 51, using the for...of loop construct with the const keyword threw a SyntaxError (\"missing = in const declaration\")."
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"version_added": false
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"version_added": true
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"opera": {
"version_added": "25"
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"version_added": "25"
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"safari": {
"version_added": "8"
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"safari_ios": {
"version_added": "8"
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"samsunginternet_android": {
"version_added": true
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"webview_android": {
"version_added": "38"
}
},
"status": {
"experimental": false,
"standard_track": true,
"deprecated": false
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},
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"__compat": {
"description": "async iterators",
"support": {
"chrome": {
"version_added": "63"
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"chrome_android": {
"version_added": "63"
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"edge": {
"version_added": null
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"edge_mobile": {
"version_added": null
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"firefox": {
"version_added": "57"
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"firefox_android": {
"version_added": "57"
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"ie": {
"version_added": null
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"nodejs": {
"version_added": null
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"opera": {
"version_added": "50"
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"opera_android": {
"version_added": "50"
},
"safari": {
"version_added": null
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"safari_ios": {
"version_added": null
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"samsunginternet_android": {
"version_added": null
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"webview_android": {
"version_added": "63"
}
},
"status": {
"experimental": false,
"standard_track": true,
"deprecated": false
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}
},
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"__compat": {
"description": "Closing iterators",
"support": {
"chrome": {
"version_added": "51"
},
"chrome_android": {
"version_added": true
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"edge": {
"version_added": true
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"edge_mobile": {
"version_added": true
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"firefox": {
"version_added": "53"
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"firefox_android": {
"version_added": "53"
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"ie": {
"version_added": false
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"nodejs": {
"version_added": true
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"opera": {
"version_added": true
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"opera_android": {
"version_added": true
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"safari": {
"version_added": true
},
"safari_ios": {
"version_added": true
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"samsunginternet_android": {
"version_added": true
},
"webview_android": {
"version_added": true
}
},
"status": {
"experimental": false,
"standard_track": true,
"deprecated": false
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}
}
},
"function": {
"__compat": {
"mdn_url": "https://developer.mozilla.org/docs/Web/JavaScript/Reference/Statements/function",
"spec_url": "https://tc39.github.io/ecma262/#sec-function-definitions",
"support": {
"chrome": {
"version_added": true
},
"chrome_android": {
"version_added": true
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"edge": {
"version_added": true
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"edge_mobile": {
"version_added": true
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"firefox": {
"version_added": "1"
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"firefox_android": {
"version_added": "4"
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"ie": {
"version_added": true
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"nodejs": {
"version_added": true
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"opera": {
"version_added": true
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"opera_android": {
"version_added": true
},
"safari": {
"version_added": true
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"safari_ios": {
"version_added": true
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"samsunginternet_android": {
"version_added": true
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"webview_android": {
"version_added": true
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"__compat": {
"description": "Allowed in sloppy mode",
"support": {
"chrome": {
"version_added": "49"
},
"chrome_android": {
"version_added": null
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"edge": {
"version_added": null
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"edge_mobile": {
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"ie": {
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"nodejs": {
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"opera": {
"version_added": true
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"opera_android": {
"version_added": null
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"safari": {
"version_added": null
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"safari_ios": {
"version_added": null
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"samsunginternet_android": {
"version_added": null
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"webview_android": {
"version_added": null
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},
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"standard_track": true,
"deprecated": false
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}
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"trailing_comma_in_parameters": {
"__compat": {
"description": "Trailing comma in parameters",
"support": {
"chrome": {
"version_added": "58"
},
"chrome_android": {
"version_added": "58"
},
"edge": {
"version_added": null
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"edge_mobile": {
"version_added": null
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"firefox": {
"version_added": "52"
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"firefox_android": {
"version_added": "52"
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"ie": {
"version_added": null
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"nodejs": {
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"opera": {
"version_added": "45"
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"version_added": "45"
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"safari": {
"version_added": null
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"safari_ios": {
"version_added": null
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"samsunginternet_android": {
"version_added": "7.0"
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"webview_android": {
"version_added": "58"
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"status": {
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"standard_track": true,
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"generator_function": {
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"description": "function*",
"mdn_url": "https://developer.mozilla.org/docs/Web/JavaScript/Reference/Statements/function*",
"spec_url": "https://tc39.github.io/ecma262/#sec-generator-function-definitions",
"support": {
"chrome": {
"version_added": "39"
},
"chrome_android": {
"version_added": "39"
},
"edge": {
"version_added": "13"
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"edge_mobile": {
"version_added": true
},
"firefox": {
"version_added": "26"
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"firefox_android": {
"version_added": "26"
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"ie": {
"version_added": false
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"nodejs": [
{
"version_added": "4.0.0"
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{
"version_added": "0.12",
"flags": [
{
"type": "runtime_flag",
"name": "--harmony"
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}
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"opera": {
"version_added": "26"
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"opera_android": {
"version_added": true
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"safari": {
"version_added": "10"
},
"safari_ios": {
"version_added": "10"
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"samsunginternet_android": {
"version_added": "4.0"
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"webview_android": {
"version_added": true
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},
"status": {
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"IteratorResult_object": {
"__compat": {
"description": "IteratorResult object instead of throwing",
"support": {
"chrome": {
"version_added": "49"
},
"chrome_android": {
"version_added": true
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"edge": {
"version_added": "13"
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"edge_mobile": {
"version_added": true
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"firefox": {
"version_added": "29"
},
"firefox_android": {
"version_added": "29"
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"ie": {
"version_added": false
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"nodejs": {
"version_added": true
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"opera": {
"version_added": true
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"opera_android": {
"version_added": true
},
"safari": {
"version_added": true
},
"safari_ios": {
"version_added": true
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"samsunginternet_android": {
"version_added": true
},
"webview_android": {
"version_added": true
}
},
"status": {
"experimental": false,
"standard_track": true,
"deprecated": false
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}
},
"not_constructable_with_new": {
"__compat": {
"description": "Not constructable with new (ES2016)",
"support": {
"chrome": {
"version_added": true
},
"chrome_android": {
"version_added": true
},
"edge": {
"version_added": null
},
"edge_mobile": {
"version_added": null
},
"firefox": {
"version_added": "43"
},
"firefox_android": {
"version_added": "43"
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"ie": {
"version_added": false
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"nodejs": {
"version_added": true
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"opera": {
"version_added": true
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"opera_android": {
"version_added": true
},
"safari": {
"version_added": "10"
},
"safari_ios": {
"version_added": "10"
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"samsunginternet_android": {
"version_added": true
},
"webview_android": {
"version_added": true
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},
"status": {
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"standard_track": true,
"deprecated": false
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}
},
"trailing_comma_in_parameters": {
"__compat": {
"description": "Trailing comma in parameters",
"support": {
"chrome": {
"version_added": null
},
"chrome_android": {
"version_added": null
},
"edge": {
"version_added": null
},
"edge_mobile": {
"version_added": null
},
"firefox": {
"version_added": "52"
},
"firefox_android": {
"version_added": "52"
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"ie": {
"version_added": null
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"opera": {
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"version_added": null
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"safari": {
"version_added": null
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"safari_ios": {
"version_added": null
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"samsunginternet_android": {
"version_added": null
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"webview_android": {
"version_added": null
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},
"status": {
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"standard_track": true,
"deprecated": false
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}
}
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"description": "if...else",
"mdn_url": "https://developer.mozilla.org/docs/Web/JavaScript/Reference/Statements/if...else",
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"support": {
"chrome": {
"version_added": true
},
"chrome_android": {
"version_added": true
},
"edge": {
"version_added": true
},
"edge_mobile": {
"version_added": true
},
"firefox": {
"version_added": "1"
},
"firefox_android": {
"version_added": "4"
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"ie": {
"version_added": true
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"nodejs": {
"version_added": true
},
"opera": {
"version_added": true
},
"opera_android": {
"version_added": true
},
"safari": {
"version_added": true
},
"safari_ios": {
"version_added": true
},
"samsunginternet_android": {
"version_added": true
},
"webview_android": {
"version_added": true
}
},
"status": {
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"standard_track": true,
"deprecated": false
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}
},
"import": {
"__compat": {
"mdn_url": "https://developer.mozilla.org/docs/Web/JavaScript/Reference/Statements/import",
"spec_url": [
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"https://tc39.github.io/ecma262/#sec-imports"
],
"support": {
"chrome": {
"version_added": "61"
},
"chrome_android": {
"version_added": "61"
},
"edge": [
{
"version_added": "16"
},
{
"version_added": "15",
"flags": [
{
"name": "Experimental JavaScript Features",
"type": "preference"
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]
}
],
"edge_mobile": {
"version_added": true
},
"firefox": [
{
"version_added": "60"
},
{
"version_added": "54",
"version_removed": "60",
"flags": [
{
"name": "dom.moduleScripts.enabled",
"type": "preference"
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]
}
],
"firefox_android": [
{
"version_added": "60"
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{
"version_added": "54",
"version_removed": "60",
"flags": [
{
"name": "dom.moduleScripts.enabled",
"type": "preference"
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]
}
],
"ie": {
"version_added": false
},
"nodejs": {
"version_added": "8.5.0",
"flags": [
{
"name": "--experimental-modules",
"type": "runtime_flag"
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],
"notes": "files must have suffix .mjs, not .js"
},
"opera": {
"version_added": "47"
},
"opera_android": {
"version_added": "47"
},
"safari": {
"version_added": "10.1"
},
"safari_ios": {
"version_added": "10.1"
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"samsunginternet_android": {
"version_added": false
},
"webview_android": {
"version_added": "61"
}
},
"status": {
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"standard_track": true,
"deprecated": false
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},
"dynamic_import": {
"__compat": {
"description": "Dynamic import",
"support": {
"chrome": {
"version_added": "63"
},
"chrome_android": {
"version_added": "63"
},
"edge": {
"version_added": false,
"notes": "See development status."
},
"edge_mobile": {
"version_added": false
},
"firefox": {
"version_added": "66",
"flags": [
{
"name": "javascript.options.dynamicImport",
"type": "preference",
"value_to_set": "true"
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],
"notes": "See bug 1517546. This flag is enabled by default on nightly builds from Nightly 67. See bug 1522491."
},
"firefox_android": {
"version_added": "66",
"flags": [
{
"name": "javascript.options.dynamicImport",
"type": "preference",
"value_to_set": "true"
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],
"notes": "See bug 1517546. This flag is enabled by default on nightly builds from Nightly 67. See bug 1522491."
},
"ie": {
"version_added": false
},
"nodejs": {
"version_added": null
},
"opera": {
"version_added": "50"
},
"opera_android": {
"version_added": "50"
},
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},
"safari_ios": {
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"version_added": null
},
"webview_android": {
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}
},
"status": {
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"standard_track": true,
"deprecated": false
}
}
}
},
"import_meta": {
"__compat": {
"description": "import.meta",
"mdn_url": "https://developer.mozilla.org/docs/Web/JavaScript/Reference/Statements/import.meta",
"spec_url": [
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],
"support": {
"chrome": {
"version_added": "64"
},
"chrome_android": {
"version_added": "64"
},
"firefox": {
"version_added": "62"
},
"firefox_android": {
"version_added": "62"
},
"ie": {
"version_added": false
},
"opera": {
"version_added": "51"
},
"opera_android": {
"version_added": "51"
},
"samsunginternet_android": {
"version_added": false
},
"webview_android": {
"version_added": "64"
}
},
"status": {
"experimental": false,
"standard_track": true,
"deprecated": false
}
}
},
"label": {
"__compat": {
"mdn_url": "https://developer.mozilla.org/docs/Web/JavaScript/Reference/Statements/label",
"spec_url": "https://tc39.github.io/ecma262/#sec-labelled-statements",
"support": {
"chrome": {
"version_added": true
},
"chrome_android": {
"version_added": true
},
"edge": {
"version_added": true
},
"edge_mobile": {
"version_added": true
},
"firefox": {
"version_added": "1"
},
"firefox_android": {
"version_added": "4"
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"ie": {
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"nodejs": {
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"opera": {
"version_added": true
},
"opera_android": {
"version_added": true
},
"safari": {
"version_added": true
},
"safari_ios": {
"version_added": true
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"samsunginternet_android": {
"version_added": true
},
"webview_android": {
"version_added": true
}
},
"status": {
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"standard_track": true,
"deprecated": false
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}
},
"let": {
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"mdn_url": "https://developer.mozilla.org/docs/Web/JavaScript/Reference/Statements/let",
"spec_url": "https://tc39.github.io/ecma262/#sec-let-and-const-declarations",
"support": {
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{
"version_added": "49"
},
{
"version_added": "48",
"version_removed": "49",
"flags": [
{
"type": "preference",
"name": "Enable Experimental JavaScript Features"
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],
"notes": "Support outside of strict mode."
},
{
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"version_removed": "49",
"partial_implementation": true,
"notes": "Strict mode is required."
}
],
"chrome_android": [
{
"version_added": "49"
},
{
"version_added": "48",
"version_removed": "49",
"flags": [
{
"type": "preference",
"name": "Enable Experimental JavaScript Features"
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],
"notes": "Support outside of strict mode."
},
{
"version_added": "41",
"version_removed": "49",
"partial_implementation": true,
"notes": "Strict mode is required."
}
],
"edge": {
"version_added": "12"
},
"edge_mobile": {
"version_added": "12"
},
"firefox": {
"version_added": "44",
"notes": [
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"Prior to Firefox 46, a TypeError is thrown on redeclaration instead of a SyntaxError.",
"Firefox 54 adds support of let in workers."
]
},
"firefox_android": {
"version_added": "44",
"notes": [
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"Prior to Firefox 46, a TypeError is thrown on redeclaration instead of a SyntaxError.",
"Firefox 54 adds support of let in workers."
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},
"ie": {
"version_added": "11"
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"nodejs": {
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},
"opera": {
"version_added": "17"
},
"opera_android": {
"version_added": "17"
},
"safari": {
"version_added": "10"
},
"safari_ios": {
"version_added": "10"
},
"samsunginternet_android": {
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"webview_android": [
{
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{
"version_added": "41",
"version_removed": "49",
"partial_implementation": true,
"notes": "Strict mode is required."
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]
},
"status": {
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"standard_track": true,
"deprecated": false
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}
},
"return": {
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"mdn_url": "https://developer.mozilla.org/docs/Web/JavaScript/Reference/Statements/return",
"spec_url": "https://tc39.github.io/ecma262/#sec-return-statement",
"support": {
"chrome": {
"version_added": true
},
"chrome_android": {
"version_added": true
},
"edge": {
"version_added": true
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"edge_mobile": {
"version_added": true
},
"firefox": {
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},
"firefox_android": {
"version_added": "4"
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"ie": {
"version_added": true
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"nodejs": {
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"opera": {
"version_added": true
},
"opera_android": {
"version_added": true
},
"safari": {
"version_added": true
},
"safari_ios": {
"version_added": true
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"samsunginternet_android": {
"version_added": true
},
"webview_android": {
"version_added": true
}
},
"status": {
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"standard_track": true,
"deprecated": false
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}
},
"switch": {
"__compat": {
"mdn_url": "https://developer.mozilla.org/docs/Web/JavaScript/Reference/Statements/switch",
"spec_url": "https://tc39.github.io/ecma262/#sec-switch-statement",
"support": {
"chrome": {
"version_added": true
},
"chrome_android": {
"version_added": true
},
"edge": {
"version_added": true
},
"edge_mobile": {
"version_added": true
},
"firefox": {
"version_added": "1"
},
"firefox_android": {
"version_added": "4"
},
"ie": {
"version_added": true
},
"nodejs": {
"version_added": true
},
"opera": {
"version_added": true
},
"opera_android": {
"version_added": true
},
"safari": {
"version_added": true
},
"safari_ios": {
"version_added": true
},
"samsunginternet_android": {
"version_added": true
},
"webview_android": {
"version_added": true
}
},
"status": {
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"standard_track": true,
"deprecated": false
}
}
},
"throw": {
"__compat": {
"mdn_url": "https://developer.mozilla.org/docs/Web/JavaScript/Reference/Statements/throw",
"spec_url": "https://tc39.github.io/ecma262/#sec-throw-statement",
"support": {
"chrome": {
"version_added": true
},
"chrome_android": {
"version_added": true
},
"edge": {
"version_added": true
},
"edge_mobile": {
"version_added": true
},
"firefox": {
"version_added": "1"
},
"firefox_android": {
"version_added": "4"
},
"ie": {
"version_added": true
},
"nodejs": {
"version_added": true
},
"opera": {
"version_added": true
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