Problems with the identification of javascript regular expressions

wmmwkiwi

<script language = "javascript">
var Re = / [0-9] /;
document.write (Re.test ("0"));
document.write (Re.test ("0"));
document.write (Re.test ("0"));
</ script>

The result is true true true;

and
<script language = "javascript">
var Re = / [0-9] / g;
document.write (Re.test ("0"));
document.write (Re.test ("0"));
document.write (Re.test ("0"));
</ script>
The result is true false true.

One [g] difference, why is this happening?

Thank you!

echosl

This result may be related to test. Each time test and exec are executed, it moves the search in the string. There is a lastindex property, which is set to the character position of the matching substring. When test is called again, the matching will be performed from lastIndex. Therefore the first test it found has a '0', so it displays 'true'. When it is used the second time, it starts from the previous position, so if it is not found, it returns 'false'. So the return is 'true'.

Without [g], test and exec will always set lastIndex to 0.

gbagbcgb

Will it happen?

zmdzff

g is global match
When a character is globally matched once, it will not be used next time
<script language = "javascript">
var Re = / [0-9] / g;
document.write (Re.test ("01"));
document.write (Re.test ("01"));
document.write (Re.test ("01"));
</ script>
Without g
Then it will match from scratch every time
So it is true every time

wmmwkiwi

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