Edit in JSFiddle

var name = 'window下的name<br/>';
var resultCon;
function fn1() {
    resultCon.innerHTML += this.name;
}

function MyObj() {
    var name = 'MyObj下的name<br/>';
    this.doFunction = function() {
        resultCon.innerHTML += this.name;
    };
}


window.onload = function() {
    resultCon = document.getElementById('result');
    var name = "onload下的name<br/>";
    var fn2 = function() {
        resultCon.innerHTML += this.name;
    };
    fn1();//window下的name
    fn2();//window下的name
    var obj = new MyObj();
    obj.doFunction();//undefined
};

<div id="result">代码输出结果：<br/></div>