测试代码如下:
<html>
<script>
var count = 0;
var number = 1000;
for (var i = 0; i < 900; i++) {
var buggyObject = {
callAgain: function() {
var ref = this;
var val = setTimeout(function() {
ref.callAgain();
var newArray = new Array();
if( count > 3)
number = 10000;
for( var a = 0; a < number; a++)
newArray[a] = a;
console.log("called");
count++;
}, 1000); // end of val declaration
} // end of call again
} // end of object declaration
}
buggyObject.callAgain();
</script>
</html>
通过tab timeline观测到在第3900ms时，系统有一个garbage collection的operation, 总共回收内存425k:
garbage collection能够生效的原因是因为在每次timer trigger并且执行完毕后，当前execution environment里的局部变量newArray 引用计数为0，因此可以被回收:
如果将该定义成局部变量的array改成全局变量，则GC不会再发生:
<html>
<script>
var count = 0;
var number = 1000;
var globalArray = [];
for (var i = 0; i < 900; i++) {
var buggyObject = {
callAgain: function() {
var ref = this;
var val = setTimeout(function() {
ref.callAgain();
if( count > 3)
number = 10000;
for( var a = 0; a < number; a++)
globalArray.push(a);
console.log("called");
count++;
}, 1000); // end of val declaration
} // end of call again
} // end of object declaration
}
buggyObject.callAgain();
</script>
</html>
