How to forEach Over an Array in JavaScript
Topic: JavaScript / jQueryPrev|Next
Answer: Use the forEach() Method
You can simply use the array's forEach() method to loop through all the items in an array using JavaScript. The forEach() method executes a provided function once for each array element.
The following example will display all the values in the cities array using foreach loop.
Example
Try this code »<script>
// Sample array
var cities = ["London", "Paris", "New York", "Amsterdam"];
// Loop over array
cities.forEach(function(value){
document.write("<p>" + value + "</p>");
});
</script>The forEach() method does not modify the original array (i.e. the array on which it is called). However, the callback function, if invoked, may do so. The following example will modify the given array by squaring each of its value (multiplying it by itself).
Example
Try this code »<script>
// Sample array
var numbers = [1, 2, 3, 4, 5, 6];
// Loop over array and squaring each value
numbers.forEach(function(value, index, array){
array[index] = value * value;
});
console.log(numbers); // Prints: [1, 4, 9, 16, 25, 36]
</script>The basic syntax of the forEach() method can be given with arr.forEach(function callback(value, index, array){ // your iterator }. The callback function is invoked with three arguments: the element value, the element index, and the array being traversed.
The forEach() was added to the ECMAScript standard in the 5th edition. This method is supported in all major modern browsers, such as Chrome, Firefox, IE9+, etc.
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