js技巧

• 定時器

setTimeout(function(num) {
        alert(num)
    }, 1000, 123);

• 字符串的拼接

window.onload = function() {
        document.body.innerHTML = '<div>div</div>\
        <span>span</span>\
        <p>p</p>\
        99999';
    }

• console.log()

 console.log('%c'+'123123123','font-size:400%;background:blue;color:#fff')

• 嵌套for循環

  a : for (var i  = 0; i < 5; i++) {
        for(var j = 0; j < 1; j++) {
            if ( i === 3) {
                break a;
            }
            alert(i);
        }
    }

• 循環的另類寫法

 var i = 0
    for (;;) {
        alert('循環的另類寫法'+i)
        if (++i >=5) {
            break;
        }
    }

• call

  var obj = {
        aaa : function() {
            alert(this);
        }
    }
    var arr = [1,2,3];
    obj.aaa();//this指向obj
    obj.aaa.call(arr);//this指向arr

• insertBefore

 var iNow = 0;
    var oBtn = document.getElementById('btn'),
        oUl = document.getElementById('list'),
        aLi = oUl.getElementsByTagName('li');
    oBtn.onclick = function() {
        var oLi = document.createElement('li');
        iNow++;
        oLi.innerHTML = iNow;
            oUl.insertBefore(oLi,aLi[0]);
    }