手寫js面試題集

sinPence發表於2019-04-11
JS面試題

  • 實現一個遍歷domtree

function domtree(dom,index=0){
	index++;//domtree深度
	if (dom.nodeType === Node.ELEMENT_NODE) {
		console.log(dom.tagName+":"+index)
	}
	let childNodes = dom.childNodes;
	for (let i=0;i<childNodes.length;i++) {
		if(childNodes[i].nodeType === Node.ELEMENT_NODE){
			domtree(childNodes[i],index)
		}
	}
}複製程式碼

  • 實現一個instanceof

先上一張圖

                        手寫js面試題集

function  Instanceof(a,b) {
	let proto = a.__proto__;
	let prototype = b.prototype;
	while (true){
		if (proto === prototype) { 
			return true
		}
		if (proto == null) {
			return false
		}
		proto = proto.__proto__;
	}
}複製程式碼

  • 防抖與節流

1.防抖
function debounce(func,wait){
	let timer = null;
	return function(...prm){
		if(timer) clearTimeout(timer);
		timer = setTimeout(()=>{
			func(...prm)
		},wait)
	}
}複製程式碼

2.節流

function throttle(fn, wait) {
	let prev = new Date();
	return function() { 
	    const args = arguments;
		const now = new Date();
		if (now - prev > wait) {
			fn.apply(this, args);
			prev = new Date();
		}
}複製程式碼

  • 深拷貝

function deepCopy(obj){
    if(typeof obj == "object"){
        var result = obj.constructor == Array ? [] : {};
        for(let i in obj){
            result[i] =  deepCopy(obj[i]) ;
        }
    }else {
        var result = obj;
    }
    return result;
}複製程式碼




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