选择题：
1、
let obj = Object.create({name: 'King'});
function foo(obj){
Object.setPrototypeOf(obj, null);
return obj;
}
console.log(obj === foo(obj)); // true
let obj = [1,2,3];
function foo(val){
val = [1,2,3];
return val;
}
console.log(obj === foo(obj)); // false
let obj = 1;
function foo(val){
val += 1;
return val;
}
console.log(obj === foo(obj)); // false
let obj = {bar: 1};
function foo(val){
val.bar += 1;
return val
}
console.log(obj === foo(obj)); // true
let obj = [1,2,3];
function foo(val){
const newVal = val.map(num => num * 2);
return newVal;
}
console.log(obj === foo(obj)); // false
let obj = [1,2,3];
function foo(val){
return val.sort();
}
console.log(obj === foo(obj)); // true
主要考察引用对象的引用地址是否相同
2、
<body> <div id="J_container"> <div id="div2"> <div id="div1">点我</div> </div> </div> <script> var div1 = document.getElementById('div1'); var div2 = document.getElementById('div2'); div1.addEventListener('click', () => {console.log('a')}, true); div2.addEventListener('click', () => {console.log('b')}); div1.addEventListener('click', () => {console.log('c')}, false); div2.addEventListener('click', () => {console.log('d')}, true); </script> </body>
输出的顺序是： d a c b
第一道编程题：
要求：
我的解答：
function cycleDetector(obj){ let stack = []; let res = false; let _incircle = function(item){ let len = stack.length; for( let y = 0; y < len; y++){ if( item === stack[y]){ return true; } } return false; } let _read = function(_obj){ for ( let pro in _obj ){ if( _obj[pro] instanceof Object ){ if ( !_incircle(_obj[pro]) ){ stack.push(_obj[pro]); _read(_obj[pro]); }else{ res = true; } } } }; _read(obj); return res; }
第二道编程题：
要求：
我的解答：
class EventEmitter { /* 在此处填写实现 */ constructor(){ this.eventlist = {}; this.onceEventlist = {}; } fire(obj){ const { type, value } = obj; let _run = 1; let _find = function(list){ for(let i in list){ if(i === type){ for(let j in list[i]){ list[i][j](value); if( _run ){ delete list[i]; } } } } _run = 0; }; _find(this.onceEventlist); _find(this.eventlist); } on(event, fn){ this.eventlist[event] = {}; this.eventlist[event][fn.name] = fn; } off(event, fn){ if(this.eventlist[event]){ delete this.eventlist[event][fn.name]; } } once(event, fn){ this.onceEventlist[event] = {}; this.onceEventlist[event][fn.name] = fn; } } const emitter = new EventEmitter(); const handler = function(evt) { console.log(1, evt); }; emitter.on('foo', handler); emitter.once('foo', function(evt) { console.log(2, evt); }); emitter.fire({ type: 'foo', value: 'hello' }); emitter.fire({ type: 'foo', value: 'world' }); emitter.off('foo', handler); emitter.fire({ type: 'foo', value: 'test' });
三、其它
一道模板解析习题
想法就是通过正则解析：
var template = function(str) { var replace = {}; var result; var newStr = str; var re = new RegExp('\<\%\=\w+\%\>','g'); while((result = re.exec(str)) !== null){ var _re = new RegExp('\w+','g'); var item = result[0].match(_re)[0]; replace[item] = {}; replace[item].origin = result[0]; } return function(obj) { for(var i in obj){ if(replace[i]){ str = str.replace(replace[i].origin, obj[i]); } } return str; } }