读书笔记-04-JavaScript语言精粹

JavaScript语言精粹

简介

对象 Object

对象 Object

函数 Function

函数 Function

继承 Inheritance

继承 Inheritance

数组 Array

数组 Arrays

正则表达式 Regular Expressions

正则表达式 Regular Expressions

方法 Methods

方法 Methods

如何实现

Array

array.pop( )

// pop可以像这样实现：
Array.method('pop',function(){
    return this.splice()(this.length - 1,1)[0]
})

array.push(item...)

// push可以像这样实现
Array.method('push',function(){
    this.splice.apply(
    	this,
[this.length,0].concat(Array.prototype.slice.apply(arguments)))
    return this.length;
})

array.shift()

Array.method('shift',function(){
    return this.splice(0,1)[0];
})

array.splice(start, deleteCount, item...)

// splice可以像这样实现：
Array.method('splice',function(start,deleteCount){
    var max = Math.max,
        min = Math.min,
        delta,
        element,
        insertCount = max(argments.length - 2, 0),
        k = 0,
        len = this.length,
        new_len,
        result = [],
        shift_count;
    
    start = start || 0;
    if(start < 0){
        start += len;
    }
    start = max(min(start,len),0);
    deleteCount = max(min(typeof deleteCount === 'number' ? deleteCount : len,len - start),0)
    delta = insertCount - deleteCount;
    new_len = len + delta;
    while(k < deleteCount){
        element = this[start + k];
        if(element !== undefined){
            result[k] = element;
        }
        k += 1;
    }
    shift_count = len - start - deleteCount;
    if(delta < 0){
        k = start + insertCount;
        while(shift_count){
            this[k] = this[k-delta];
            k +=1;
            shift_count -= 1;
        }
        this.length = new_len;
    }else if(delta>0){
        k = 1;
        while(shift_count){
            this[new_len - k] = this[len - k];
            k += 1;
            shift_count -= 1;
        }
        this.length = new_len;
    }
    for(k = 0; k< insertCount; k+=1){
        this[start += k] = arguments[k + 2];
    }
    return result;
})

array.unshift(item...)

// unshift可以像这样实现：
Array.methods('unshift', function(){
    this.splice.apply(this,[0,0].concat(Array.prototype.slice.apply(arguments)));
    return this.length;
})

RegExp

regexp.test(string)

// test可以像这样实现：
RegExp.method('test',function(string){
    return this.exec(string) !== null;
})

Srting

string.charAt(pos)

// charAt可以像这样实现：
String.method('charAt',function(pos){
    return this.splice(pos,pos+1);
})

代码风格 Style

代码风格优美的特性

毒瘤&糟粕

毒瘤&糟粕