JavaScript之apply模擬實現

JavaScript之apply模擬實現

apply的實現跟call相似

 

ES5的實現

Function.prototype.apply2=function(context,arr){
    var context = context || window
    context.fn = this
    var result
    if(!arr){
         result = context.fn()
    }else{
         var args = []
         for(var i=0;i < arr.length; i++) {
             args.push('arr['+i+']')
         }
         result = eval('context.fn('+args+')')
    }
    delete context.fn
    return result
}

ES6實現

Function.prototype.apply2 = function(context,arr){
    context = context || window
    context.fn = this
    let result
    if(!arr){
        result = context.fn()
    }else{
        let args = []
        for(let i=0; i<arr.length; i++) {
            args.push(arr[i])
        }
        result = context.fn(...args)
    }
    delete context.fn
    return result
}