<!doctype html>
<meta charset="utf-8">
<title>Behavior of iterators when modified within foreach</title>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<link rel="help" href="https://webidl.spec.whatwg.org/#es-forEach">
<link rel="author" title="Manish Goregaokar" href="mailto:manishsmail@gmail.com">
<script>
test(function() {
    let params = new URLSearchParams("a=1&b=2&c=3");
    let arr = [];
    params.forEach((p) => {
        arr.push(p);
        params.delete("b");
    })
    assert_array_equals(arr, ["1", "3"]);
}, "forEach will not iterate over elements removed during iteration");
test(function() {
    let params = new URLSearchParams("a=1&b=2&c=3&d=4");
    let arr = [];
    params.forEach((p) => {
        arr.push(p);
        if (p == "2") {
            params.delete("a");
        }
    })
    assert_array_equals(arr, ["1", "2", "4"]);
}, "Removing elements already iterated over during forEach will cause iterator to skip an element");
test(function() {
    let params = new URLSearchParams("a=1&b=2&c=3&d=4");
    let arr = [];
    params.forEach((p) => {
        arr.push(p);
        if (p == "2") {
            params.append("e", "5");
        }
    })
    assert_array_equals(arr, ["1", "2", "3", "4", "5"]);
}, "Elements added during iteration with forEach will be reached");
</script>
