window.onload=function () {
var echo = document.write;
document.write = function ()
{
alert('此方法,已经被重写')
}
function showezi (){
var birth = 1998;
var y = new Date().getFullYear();
return y - this.birth;
}
echo ('123')
} 报错内容 :javascript.js:16 Uncaught TypeError: Illegal invocation,如果我把上面的document.write换成alert;就可以赋值alert方法,但是document.write就不行呢。各位老师帮我看一下吧。
window.onload=function () {
var echo = document.write; document.write = function () { alert('此方法,已经被重写') }
function showezi (){ var birth = 1998; var y = new Date().getFullYear(); return y - this.birth; }
echo ('123')
}
我的报错信息是这样的:
window.onload=function ()
{
var echo = document.write;
document.write = function ()
{
alert('此方法,已经被重写')
}
VM23013:7 Uncaught SyntaxError: Unexpected end of input
function showezi (){
var birth = 1998;
VM23083:2 Uncaught SyntaxError: Unexpected end of input
var y = new Date().getFullYear();
undefined
return y - this.birth;
VM23159:1 Uncaught SyntaxError: Illegal return statement
}
VM23163:1 Uncaught SyntaxError: Unexpected token }
echo ('123')
VM23187:1 Uncaught ReferenceError: echo is not defined
at <anonymous>:1:1
(anonymous) @ VM23187:1
- 1
苹果熊
实际上,JavaScript默认有一个全局对象window。 这个说法有点不严谨吧,应该要加个具体环境。Node环境里就没有window对象了