function add(x,y){ return x + y};

var myObject = {
    value: 0,increment: function (inc) {
        this.value += typeof inc === 'number' ? inc : 1;
    }
};

myObject.increment(2);
document.writeln(myObject.value); 

myObject.double = function (  ) {
    var that = this;    // Workaround.

    var helper = function (  ) {
        that.value = add(that.value,that.value)
    };

    helper(  );    // Invoke helper as a function.
};

myObject.double(  );
document.writeln(myObject.value);    // 4

对于函数调用模式,’this’对象将具有全局引用.但我不能完全理解所提到的解决方案的引擎盖： –

var that = this;    // Workaround.

如果我们这样做,我们不是只是将’this’的引用复制到’that’吗？即’that’将与’this’一样保持全球范围？这在内部如何运作？