168.[JavaScript]手写call,apply,bind

[webVueBlog]

[js]

[webVueBlog]

/**
 * call
 */
Function.prototype.myCall = function (context = window,...args) {
    if(this === Function.prototype) {
        return undefined
    }
    context = context || window
    const fn = Symbol();
    context[fn] = this;
    const result = context[fn](...args);
    delete context[fn]
    return result 
}
/**
 * apply
 */

Function.prototype.myApply = function (context = window,args) {
    if(this === Function.prototype) {
        return undefined
    }
    const fn = Symbol();
    context[fn] = this;
    let result;
    if(Array.isArray(args)) {
        result = context[fn](..args);
    }else {
        result = context[fn]()''
    }
    delete context[fn]
    return result
}
/**
 * bind
 */

Function.prototype.myBind = function (context, ...args1) {
    if(this === Function.prototype) {
        throw new TypeError('Error')
    }
    const _this = this;
    return function F(...args2) {
        if(this instanceof F) {
            return new _this(...args1,...args2)
        }
        return _this.apply(context,args1.concat(args2))
    }
}