Javascript：如何编写正则表达式来检查符号是否被所有出现的空格包围

Question

The colon ':' in the sentence should be surrounded by space for all of its occurrences.

I have a string "Yes I Do : things that have:fun"

My regex should return false, I have tried the below which is checking is checking first occurence, if found it is returning true.

/(\s:\s)/.test("sd : sds:sds")

Answer 1

If you want a pure regex solution then use this alternation based regex to find out invalid inputs :

/(?:^|\S):|:(?:$|\S)/

RegEx Demo

RegEx Details:

• (?:^|\\S) : Match start or a non-whitespace
• : : Match a colon
• | : OR
• : : Match a colon
• (?:$|\\S) : Match end or a non-whitespace

 const regex = /(?:^|\\S):|:(?:$|\\S)/; const arr = [`Yes I Do : things that have :fun`, `Yes I Do : things that have: fun`, `: fun`, `fun :`, `Yes I Do : things that have : fun`, ` : fun`, `fun : `]; for (var i=0; i<arr.length; i++) { console.log(regex.test(arr[i]), '::', arr[i]); }

Answer 2

你可以做完全相反的事情，搜索被非空格字符包围的符号（在符号之前或之后）。

!/\S:|:\S/.test("sd : sds:sds")

Answer 3

Add the global flag ( g ) to the end of your RegEx and check for non-space chars.

 console.log(!/\\S:|:\\S/g.test("sd : sds:sds")); console.log(!/\\S:|:\\S/g.test("sd : sds : sds"));

This will check the full string.

Answer 4

You can achieve it by regex and simple logic. This is not the proper way to achieve use case but maybe it can help.

 function check(str) { let reg = / : /gi; let match = str.match(reg); if (match && match.length == str.split(":").length - 1) { return true; } else { return false } } console.log(check("sdf : sdf")); console.log(check("sdf: sdf")); console.log(check("sdf : sdf:")); console.log(check("sdf : sdf sdfds : sdf"));