var matches;
while(matches = /./g.exec("abc"))
{
console.log("hey");
}
This never terminates. I expect it to terminate after 3 loops.
Warning: Don't run it in Chrome because the infinite log lines freeze your entire system. It's safe to run it in IE (it still freezes your webpage but you can go to the location bar and press enter to reload).
This is how you should execute exec in a loop:
var matches;
var re = /./g;
while(matches = re.exec("abc")) {
if (matches.index === re.lastIndex)
re.lastIndex++;
console.log("hey");
}
Keep regex in a separate variable rather than using regex literal.
Also if lastIndex (matched position) of regex is same as index property of resulting array then increment lastIndex by 1.
lastIndex? exec() does that for me.
It's because you are creating a new object with the g flag every time, instead of keeping one regex object. The regex object keeps track of the last match. Since you are creating new objects every time, the object starts from the beginning.
Each regex literal is it's own object that's why:
/./g !== /./g
matches = /./g.exec("abc")will return ['a'] which is a truthy value in JS, hence it runs into an infinite loop. It's likewhile(true){ // dosomething }. As the condition evaluates to true in every iteration, it will never breakgflag, each iteration is supposed to start where the previous one ended."abc"with a fresh regexp each time. For sure this is not what was intended, but you have to observe where the regexp is created and compiled. Even if javascript optimices this to create and compile the regexp only once, the matching status or history must be renewed each time you go through the test.