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Check if startsWith is configurable #702

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Check if startsWith is configurable #702

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28 changes: 15 additions & 13 deletions packages/core-js/modules/es.string.starts-with.js
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Original file line number Diff line number Diff line change
Expand Up @@ -8,16 +8,18 @@ var correctIsRegExpLogic = require('../internals/correct-is-regexp-logic');
var nativeStartsWith = ''.startsWith;
var min = Math.min;

// `String.prototype.startsWith` method
// https://tc39.github.io/ecma262/#sec-string.prototype.startswith
$({ target: 'String', proto: true, forced: !correctIsRegExpLogic('startsWith') }, {
startsWith: function startsWith(searchString /* , position = 0 */) {
var that = String(requireObjectCoercible(this));
notARegExp(searchString);
var index = toLength(min(arguments.length > 1 ? arguments[1] : undefined, that.length));
var search = String(searchString);
return nativeStartsWith
? nativeStartsWith.call(that, search, index)
: that.slice(index, index + search.length) === search;
}
});
if(Object.getOwnPropertyDescriptor(String.prototype, "startsWith").configurable) {
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If the property is not configurable, do nothing since it is going to fail anyway with an exception

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When would it not be configurable?

// `String.prototype.startsWith` method
// https://tc39.github.io/ecma262/#sec-string.prototype.startswith
$({ target: 'String', proto: true, forced: !correctIsRegExpLogic('startsWith') }, {
startsWith: function startsWith(searchString /* , position = 0 */) {
var that = String(requireObjectCoercible(this));
notARegExp(searchString);
var index = toLength(min(arguments.length > 1 ? arguments[1] : undefined, that.length));
var search = String(searchString);
return nativeStartsWith
? nativeStartsWith.call(that, search, index)
: that.slice(index, index + search.length) === search;
}
});
}