console.log.js

function connect(scope, fnFrom, fnTo) {
    "use strict"
    var objFn = fnFrom.split('.');//处理传入的函数名
    var deepth = objFn.length;
    var scope = scope || window;
    var j = deepth,i=j;
    var _obj = scope,__obj=_obj ;
    while (i > 0) {//以window.console.log为例，这里利用迭代最终拿到log
        _obj = _obj[objFn[deepth - i]];
        i -= 1;
    };
    var t = function () {
            var ret = _obj.apply(this, arguments);//此时this指向console  注意console.log  log函数上下文必须在console那里，否则会报错
            fnTo.apply(this, arguments);
            return ret;
    }
    while (j > 1) {//仍然利用迭代，找出window.console.log前一级window.console的引用
        __obj = __obj[objFn[deepth - j]];
        j -= 1;
    }
    __obj[objFn[deepth - 1]] = t;//覆盖window.console.log
}

function unconnect(scope,fn){
var objFn = fn.split('.');//处理传入的函数名
    var deepth = objFn.length;
    var scope = scope || window;
    var j = deepth,i=j;
    var _obj = scope;
      while (i > 0) {//以window.console.log为例，这里利用迭代最终拿到log
        _obj = _obj[objFn[deepth - i]];
        i -= 1;
    };
delete _obj
}

function publishConsole(inner){
    document.write(inner)
}

//start
unconnect(window,'console.log')
connect(window,'console.log',publishConsole)