JavaScript Array keys() Method
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JavaScript Array keys() Method
The keys()
method returns a new Array Iterator object that contains the keys for each index in the array.
Example
HTML Online Editor
<!DOCTYPE html>
<html>
<body>
<script>
var myFruit = ["Apple", "Banana", "Jackfruit"];
var iterator = myFruit.keys();
for(let key of iterator)
document.write(key + "<br>");
</script>
</body>
</html>
Syntax
Array.keys()
keys() for Associative Array
The keys()
method doesn't work with associative array
HTML Online Editor
<!DOCTYPE html>
<html>
<body>
<script>
var myFruit = [];
myFruit["red"] = "Apple";
myFruit["yellow"] = "Banana";
myFruit["green"] = "Jackfruit";
var iterator = myFruit.keys();
for(let key of iterator)
document.write(key + "<br>");
</script>
</body>
</html>
keys() for Map
Use Map
instead of associative array.
HTML Online Editor
<!DOCTYPE html>
<html lang="en-US">
<body>
<script>
var myFruit = new Map([
['red', 'Banana'],
['yellow', 'Guest'],
['green', 'Jackfruit'],
]);
var iterator = myFruit.keys();
for(let key of iterator)
document.write(key +"<br>");
</script>
</body>
</html>
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