JavaScript Global method: eval()
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The JavaScript
Global
eval() method evaluates or
executes an expression or set of JavaScript statements.
It
has the following syntax with the following parameters:
eval(str)
|
Parameter
|
Required / Optional
|
Description
|
|
str
|
Required
|
String representing an
expression or set of statements to evaluate / execute. If the argument is not
a string, then it is left unchanged.
|
It is not appropriate to
call eval() to evaluate an
arithmetic expression, as JavaScript evaluates such expressions automatically.
eval() should be called sparingly. For example, it
executes codes passed to it with the privileges of the calling algorithm, which
can be exploited by a malicious party. It also invokes the JavaScript
interpreter, which can frustrate modern browsers’ ways of optimising code
execution.
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>
document.getElementById("Example").innerHTML =
'var x = eval("var a = 10; var b = 2; a * b");'
document.getElementById("Result").innerHTML = eval("var a = 10; var b = 2; a * b");
</script>
</body>
</html>
|
FUNCTION THAT MAY ASSIST IN TESTING WHETHER FEATURE IS SUPPORTED:
function isSupportedJavaScriptMethodGlobalEval() {
return (eval("var a = 10; var b = 2; a * b") == 20);
} |
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