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JavaScript Array method: every()

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The every() method (when applied to a JavaScript array) returns true if every element passes a specified test, otherwise returns false. It only executes until the function it uses returns a false value and then returns false. It does not execute the function for array elements without values. It does not change the original array

 

It has the following syntax with the following parameters. It returns a Boolean as above.

 

array.every(function(currentValue, index, arr), thisValue)

 

Parameter

Required / Optional

Description

function(currentValue, index, arr)

Required

A function to be run for each element

thisValue

Optional

A value to be passed to the function to be used as its ‘this’ value (if empty then thisValue will be undefined

 

The function arguments are:

 

Parameter

Required / Optional

Description

currentValue

Required

The value of the current element

Index

Optional

The array index of the current element

arr

Optional

The array object which the current element belongs to

 

EXAMPLE:


HTML USED IN THIS EXAMPLE:
<!DOCTYPE html>
<html> <!-- Copyright (c) Nematrian Limited 2018 -->
<head>
<style>
table,th,tr,td {border: 1px solid black; border-collapse: collapse;}
</style>
</head>
<body>
<table>
<tr>
<th>Example</th>
<th>Resulting value of <code>x</code></th>
</tr>
<tr>
<td><code id="Example"></code></td>
<td><code id="Result"></code></td>
</tr>
</table>

<script>
var h = [-1, 2, 3];
document.getElementById("Example").innerHTML =
  'var h = [-1, 2, 3];<br>' +
  'function positive(x) {<br>' +
  '&nbsp;&nbsp;return x > 0;<br>' +
  '}<br>' +
  'var x = h.every(positive);';
document.getElementById("Result").innerHTML = h.every(positive);

function positive(x) {
  return x > 0;
}
</script>

</body>
</html>

FUNCTION THAT MAY ASSIST IN TESTING WHETHER FEATURE IS SUPPORTED:
function isSupportedJavaScriptMethodArrayEvery() {
  var h = [1, 2, 3]; return !!h.every;
}


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