Javascript正则表达式只替换第一个字符[重复]

Question

This question already has an answer here:

• Remove first character from a string if it is a comma 4 answers

I'm sorry if I'm to noob to ask this, but I really dont have any idea with this.

Is there any idea for regex to replace a char that stand on the first? Example :

12
13
14
15
51
41
31
21

All data that had '1' on the first char, must be replaced to 'A', example:

A2
A3
A4
A5
51
41
31
21

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Answer 1

In JavaScript :

var str = "12";
str = str.replace(/^1/, 'A');

In PHP :

$str = "12";
$str = preg_replace("/^1/","A",$str);

^ matches the start of the string.