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<html>
<script>
function A() {}
var a = new A();
alert(a instanceof A);//true
</script>
<script>
function A() {}
alert(typeof a);//object
alert(a instanceof A);//false
</script>
</html>
<script>
b=135;
function A() {
this.say = function(){alert(1)};
}
var a = new A();
a.say();// 1
alert(a instanceof A);//true
</script>
<script>
function A() {
this.say = function(){alert(2)};
}
alert(typeof a);//object
alert(a instanceof A);//false
a.say();// 1
var b;
alert(b);
</script>
<script>
function A() {
this.say = function(){alert(1)};
}
var a = new A();
a.say();// 1
alert(a instanceof A);//true
</script>
<script>
function A() {
this.say = function(){alert(2)};
}
alert(typeof a);//object
alert(a instanceof A);//false
a.say();// 1
</script>
<script>
function A() {
this.say = function(){alert(1)};
}
var a = new A();
a.say();// 2
alert(a instanceof A);//true
function A() {
this.say = function(){alert(2)};
}
alert(typeof a);//object
alert(a instanceof A);//true
a.say();// 2
</script>
<script>
//scope1 作用域1
function A() {
this.say = function(){alert(1)};
}
var a = new A();
a.say();// 1
alert(a instanceof A);//true
(function(){
//scope2 作用域2
function A() {
this.say = function(){alert(2)};
}
alert(typeof a);//object
alert(a instanceof A);//false
a.say();// 1
})()
</script>