Finding Plus Sign in Regular Expression

Question

var string = \'abcd+1\';
var pattern = \'d+1\'
var reg = new RegExp(pattern,\'\');
alert(string.search(reg));

I found out last night that if you tr

Answer 1

It should be var pattern = '/d\\+1/'.

The string will escape '\\' as '\' ('\\+' --> '\+') so the regex object init with /d\+1/

Answer 2

You should use the escape character \ in front of the + in your pattern. eg. \+

Answer 3

\-\.\/\[\]\\ **always** need escaping
\*\+\?\)\{\}\| need escaping when **not** in a character class- [a-z*+{}()?]

But if you are unsure, it does no harm to include the escape before a non-word character you are trying to match.

A digit or letter is a word character, escaping a digit refers to a previous match, escaping a letter can match an unprintable character, like a newline (\n), tab (\t) or word boundary (\b), or a a set of characters, like any word-character (\w), any non-word character (\W).

Don't escape a letter or digit unless you mean it.

Answer 4

Just a note,

\ should be \\ in RegExp pattern string, RegExp("d\+1") will not work and Regexp(/d\+1/) will get error.

var string = 'abcd+1';
var pattern = 'd\\+1'
var reg = new RegExp(pattern,'');
alert(string.search(reg));
//3

Answer 5

Plus is a special character in regular expressions, so to express the character as data you must escape it by prefixing it with \.

var reg = /d\+1/;

Answer 6

Easy way to make it :

The alphabet is : "[\+]"

All plus signs we want to find : "[\+]*"