Add more than one variable in Javascript to work with the RegEx function

Question

This post details how to include variables in regular expressions, but it only shows how to include one variable. I am currently using the match function for a regular expression to find the string in between a leading and trailing string. My code is below:

array = text.match(/SomeLeadingString(.*?)SomeTrailingString/g);

Now, how could I construct a regular expression that has the same functionality as this, but rather than having the two strings I'm using actually in the expression, I would like to be able to create them outside, like so:

var startString = "SomeLeadingString"
var endString = "SomeTrailingString"

So, my final question is, how can I include startString and endString into the regular expression that I listed above so that the functionality is the same? Thanks!

Answer 1

Use RegExp object to concatenate strings to regex

const reg = new RegExp(`${startString}(\\w+)${endString}`,"g");
const matches = text.match(reg);

Note

When concatenating string, it is recommended to escape the none regex string: (the escape pattern is taken from this answer)

const escapeReg = (str)=>str.replace(/[-\/\\^$*+?.()|[\]{}]/g, '\\$&');

Example

We have the string (.*)hello?? and we want to match the word between the (.*) and ??

we will do something like:

const prefix = "(.*)";
const suffix = "??";
const reg = new RegExp(`${escapeReg(prefix)}(\\w+)${escapeReg(suffix)}`);
const result = "(.*)hello??".match(reg);
if(result){
   console.log(result[1]); //"hello"
}