练习笔记

// 实现一个函数clone
    function clone(obj){
        var o;
        switch(typeof obj){
            case 'undefined':
                break;
            case 'string':
                o = obj +"";
                break;
            case 'number':
                o = obj-0;
                break;
            case 'boolean':
                o = obj;
                break;
            case 'object':
                if(obj == null){
                    o = null;
                }else{
                    if(Object.prototype.toString.call(obj).slice(8,-1) == 'Array'){
                        o = [];
                        for (var i = 0; i < obj.length; i++) {
                            o.push(obj[i]);
                        }
                    }else{
                        o = {};
                        for(var key in obj){
                            o[key] = obj[key];
                        }
                    }
                }
                break;
            default :
                o = obj;
                break;
        }
        return o;
    }
    var obj = {
      a:"weew",
      b:122,
      c:"jjjj"
    }
    clone(obj);

    //数组去重复
    function filterAgain(arr){
        if(arr.length<1){
            return arr;
        }else{
            for (var i = 0; i < arr.length; i++) {
                if(arr.indexOf(arr[i]) != i){
                    arr.splice(i,1);
                    i--;
                }
            }
            return arr;
        }
    }

    //统计字符中每个出现的次数
    var str = "aaaabbbbcccgh";
    var obj = {};
    for (var i = 0; i < str.length; i++) {
        var v = str.charAt(i);
        if(obj[v] && obj[v].value == v){
            obj[v].count = ++ obj[v].count;
        }else{
            obj[v] = {};
            obj[v].value = v;
            obj[v].count = 1;
        }
    }
    for(var k in obj){
        document.write(obj[k].value +"="+obj[k].count+'&nbsp;');
    }
    //去除字符串前后的空白字符
    function trim(str){
        if(str && typeof str == 'string'){
            str.replace(/(^\s*)|(\s*)$/g,"");
        }
    }