正则表达式为以0开头但不是十进制的数字

Question

I am trying to write a regex for a number that starts with 0 but shouldn't match for decimals eg the regex should match 00909,050,000033 but shouldn't match 0.909 . This is the regex I used:

/[0]+\d+(?!\.)/g 

It is flawed because it matches 0.909 which is not what I want. Also, if I have a string like 0009+045*0.909 , the regex should match 0009 and 045 but not 0.909 .

I appreciate anyone with a solution for this.

Answer 1

You can use the following regex to achive what you wanted,

/^0[0-9]+/g

The above will select a number in this pattern,

• string should start with 0 .
• And followed by 1 or more continuous numbers.

And the above mentioned regex can also be written as,

/^0\d+/g

Answer 2

/\D*(0\d+?)\D*/g

这将提取模式的所有实例，这些实例可作为$ 1 ... $ 9使用

Answer 3

You can try to add a word boundary to the start of your pattern ( demo ):

/\b0+\d+\b(?!\.)/g
 ^^

See the regex demo. However, it will also fail to match numbers at the end of a sentence before the final dot. Then, use a more precise lookahead to fail matches before a . followed with a digit:

/\b0+\d+\b(?!\.\d)/g
         ^^^^^^^^ 

See this regex demo

But the safest way (in case the number looks like 4.05 ) is to use a more sophisticated pattern (to be used with RegExp#exec() in a loop to extract match[1] value):

/(?:^|[^\d.])(0+\d+)\b(?!\.\d)/g

See the regex demo

Details:

• (?:^|[^\\d.]) - non-capturing group matching the start of string or a non-digit and non-dot character
• (0+\\d+)\\b - 1+ zeros followed with 1+ digits (a whole word)
• (?!\\.\\d) - not followed with a . + a digit.

Code:

 var re = /(?:^|[^\\d.])(0+\\d+)\\b(?!\\.\\d)/g; var str = 'should match \\n00909\\n050\\n000033\\n0009\\n045\\n0009+045\\n but shouldn\\'t match\\n0.909\\n4.05'; var res = []; while ((m = re.exec(str)) !== null) { res.push(m[1]); } document.body.innerHTML += "<pre>" + str + "</pre>"; document.body.innerHTML += "<pre>" + JSON.stringify(res, 0, 4) + "</pre>"; 

Answer 4

All you have to do is constrain the boundaries from not matching a
dot nor digit before and after. The middle will then be valid.

Answer in capture group 1.

(?:^|[^\\d.])(0\\d+)(?![\\d.])

 (?: ^ | [^\d.] )          # BOS or not digit nor dot
 ( 0 \d+ )                 # (1), Number that starts with 0
 (?! [\d.] )               # Not digit nor dot