[interview] #js

array.js

Array.prototype._map = function(fn, bindThis) {
    bindThis = bindThis || null;
    return this.reduce(function(total, curr, currIndex, arr){
        // console.log(total)
        total.push(fn.call(bindThis, curr, currIndex, arr));
        return total;
    }, [])
};

Array.prototype._filter = function(fn, bindThis) {
    bindThis = bindThis || null;
    return this.reduce(function(total, curr, currIndex, arr){
        if(fn.call(bindThis, curr, currIndex, arr)) {
            total.push(curr);
        }
        return total;
    }, [])
};

var arr = [1,3,4,2];

var ret = arr._map(function(item, index){
    return item += 1;
});

var ret = arr._filter(function(item, index){
    return item == 1;
});

console.log(ret);

class.js

// https://www.cnblogs.com/mackxu/archive/2013/03/24/inherit0.html inherit函数 代码更加严谨一点

function inherit(Child, Parent){
    function f(){};
    f.prototype = Parent.prototype;
    Child.prototype = new f();

    Child.constructor = Child;
}

// new的实现
// var object = {
//     __proto__: F.prototype
// }
// F.bind(object, args);

curry

function curry(fn, ...args1){
    if(args1.length >= fn.length) {
        return fn(...args1);
    }
    return function(...args2){
        return curry(fn, ...args1, ...args2);
    }
}

function add(x, y, z){
    return x + y + z;
}

var addTen = curry(add, 10);
var addTweleve = addTen(2);
console.log(addTweleve(2));

debounce.js

function debounce(func, wait){
    let timer = null;
    return function(){
        var context = this;
        var args = [].slice.call(arguments, 0);

        clearTimeout(timer);

        timer = setTimeout(()=>{
            func.apply(context, args);
        }, wait);
    }
}

let func = debounce((value)=>{
    console.log(value);
}, 1000);

func(123);
func(1234);

string.js

String.prototype.trim = function(){
    return this.replace(/(^\s+|\s+$)/g, '');
}

var string = ' 222121 22 1';

console.log(string.trim());

throttle.js

// 1 使用timer版本
// function throttle(func, wait){
//     wait = wait || 0;
//     var timer = null;
//     var queue = [];
//     return function(...args){
//         var context = this;
//         if(timer) return;
//         let result = func.apply(context, args);
//         timer = setTimeout(function(){
//             timer = null;
//         }, wait);
//         return result;
//     }
// }

// 2 采用记录时间版本
function throttle(func, wait){
    wait = wait || 0;
    var lastCallTime = 0;
    var queue = [];
    return function(...args){
        var context = this;
        if(lastCallTime + wait < Date.now()) {
            lastCallTime = Date.now();

            let result = func.apply(context, args);
            return result;
        }
    }
}

// 3 队列中的函数仍然会执行，并有cancel函数的

var log = throttle((args)=>{
    console.log(args)
}, 1000);

log(1);
setTimeout(()=>{
    log(2);
}, 1000);