Function

函数防抖

<input type="text" name="" value="">
<script type="text/javascript">
    let el = document.querySelector('input')
    el.addEventListener("input", debounce(A, 500))

    function debounce(fn, delay) {
        let timer = null
        return function () {
            timer && clearTimeout(timer)
            timer = setTimeout(() => {
                fn.call(this)
            }, delay)
        }
    }

    function A() {
        console.log(this.value)
    }
</script>

函数节流

function throttle (fn, time = 1000) {
    let canRun = true;
    return function () {
        if (!canRun) return false;
        canRun = false;
        setTimeout(() => {
            fn.call(this)
            canRun = true
        }, time)
    }
}

setInterval(throttle(function() {
    console.log("hello world")
}), 100)

实现bind函数

Function.prototype.bind = function (context, ...args) {
    return (...newArgs) => {
        return this.call(context, ...args, ...newArgs)
    }
}

实现call/apply函数

Function.prototype.call = function (context, ...args) {
    // context为null时，context设置为window
    context = context || window
    context.fn = this
    let result = context.fn(...args)
    delete context.fn
    return result
}

// apply 只需要把参数修改即可
Function.prototype.apply = function (context, args) {
    context = context || window
    context.fn = this
    let result = context.fn(...args)
    delete context.fn
    return result
}

递归

递归是很常见的，有的时候递归的写法会有微妙的差别。拿多维数组的扁平化举例。

// 外部函数获取内部函数的返回值
function flatter(arr) {
    let newArr = []
    arr.forEach(item => {
        if (Array.isArray(item)) {
            // newArr.push(...flatter(item))
            newArr = newArr.concat(flatter(item))
        }
        else {
            newArr.push(item)
        }
    })
    return newArr
}

// 将值当作递归函数的参数
function flatter(arr, newArr = []) {
    arr.forEach(item => {
        if (Array.isArray(item)) {
            flatter(item, newArr)
        } else {
            newArr.push(item)
        }
    })
    return newArr
}