how to pass a variable into an regular expression in javascript [duplicate]

Answer 1

numLength[0] is 5. We can not add evaluation of variable in regular expression. Below code returns true.

var result = /^[-+]?\d{0,x}(\.\d{0,5})?$/.test(number);

Answer 2

try this:

<script type="text/javascript">
function xyz(){
var predefLength = "5,5";
var number = "20";
var numLength = predefLength.split(",");

var pattern = new RegExp('^[-+]?\\d{0,'+numLength[0]+'}(\\.\\d{0,'+numLength[1]+'})?$');
var result = pattern.test(number);
document.write(result);
}
</script>

Answer 3

Use the RegExp-constructor, like:

var pattern = new RegExp('pattern as a string', 'flags as a string');

Or:

var result = new RegExp('^[-+]?\d{0,' + numLength[0] + '}(\.\d{0,' + numLength[1] + '})?$').test(number);