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[英]Use Object method in anthor object without using new keyword in javascript
[英]Object() without the new keyword or .create method
我在MDN上尋找Array.prototype.includes()的polyfill,然后遇到以下Object()語法:
if (!Array.prototype.includes) {
Array.prototype.includes = function(searchElement /*, fromIndex*/) {
'use strict';
if (this == null) {
throw new TypeError('Array.prototype.includes called on null or undefined');
}
//This is the line in question
var O = Object(this);
var len = parseInt(O.length, 10) || 0;
if (len === 0) {
return false;
}
var n = parseInt(arguments[1], 10) || 0;
var k;
if (n >= 0) {
k = n;
} else {
k = len + n;
if (k < 0) {k = 0;}
}
var currentElement;
while (k < len) {
currentElement = O[k];
if (searchElement === currentElement ||
(searchElement !== searchElement && currentElement !== currentElement)) { // NaN !== NaN
return true;
}
k++;
}
return false;
};
}
在這種情況下,對象(對象)在做什么,目的是什么?
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