How can I replace strings between <!-- comment --> with something else

Question

I am using gulp to facilitate my frontend deployment. I would like to replace some strings in index.html For example, turning the following code like

<!-- js starts -->
<script src="xxxxxx/xxxx/xxx1.js"></script>
<script src="xxxxxx/xxxx/xxx2.js"></script>
<script src="xxxxxx/xxxx/xxx3.js"></script>
<script src="xxxxxx/xxxx/xxx4.js"></script>
<!-- js ends -->

into

<!-- js starts -->
<script src="xxxxxx/xxxx/all-one.js"></script>
<!-- js ends -->

I have installed gulp-string-replace, and it works fine with some simple regular expression. But my case seems contains some special characters, such as < ! -- >

This is my gulp code but not implemented what I want. gulp.src('index.html').pipe( replaceString("(?<='')(.*)(?='')", "what I want") ).pipe( gulp.dest(target) );

Answer 1

Assuming that you always keep the text in the start and end comments the same, this works:

var gulp = require('gulp');
var replaceString = require('gulp-string-replace');

let replacement = 'Hello world!';
let pattern = /(<!-- js starts -->)[^!]+(<!-- js ends -->)/gim;

gulp.src('index.html')
    .pipe(replaceString(pattern,function(n0,n1,n2){
        return n1 + '\n' + replacement + '\n' + n2;
    }))
    .pipe(gulp.dest('output'));

Result of output/index.html :

<!-- js starts -->
Hello world!
<!-- js ends -->

By the way, you said you were trying to use Regex, but it looks like you were passing in a string literal, not a Regex literal (what I use above), or the result of calling the RegExp constructor, like var pattern = new RegExp('hello\\s{0,1}World');

---

Although I won't give advice on what you should and shouldn't use, I will point out that gulp-string-replace has not been updated for a while, and has an open issue that actually affected my answer; I tried to use inline back-references (eg $1\\nHello World\\n$2 ) and it did not work, forcing me to use the callback function argument. gulp-string-replace just uses replacestream for the actual replacement operation.