How to use indexOf with multiple instances of a string pattern?

Question

How can I use String.prototype.indexOf() to find one or more matching string patters within a given string?

For example:

I have a string to test: /accounts/{account}/project/{project}
I want to test for the existence of one or more string patterns of {...} where ... could have anything. In this example they are: account, project
I would like to String.prototype.indexOf() to retrieve an Object that has a collection of start and end indexes for each instance of the matched pattern. In this example I would like to have: [{ start: 10, end: 18},{start: 28, end: 36}]

I've been able to make an object when there is just one match, but I am unsure how to get for multiple.

Also, please elaborate on your objective. If you're trying to parse a URL on the server side (e.g., with Node.js), there may be built-ins that can do it for you (route parameters and req.params, for instance). — IronFlare
– IronFlare, Commented Aug 16, 2019 at 14:49
@IronFlare - Actually, route.parameters is what I am trying to accomplish. I was trying to make something myself to use client-side. I am probably over-complicating this instead of using what you suggested. I was just trying to see if I could make my own solution. — Jason Ayer
– Jason Ayer, Commented Aug 16, 2019 at 15:43

User863 · Accepted Answer · 2019-08-16 15:34:43Z

Using replace() method

var stringUnderTest = "/accounts/{account}/project/{project}"; var result = []; stringUnderTest.replace(/\{([^\}]*)\}/gi, function(match, p1, index) { result.push({ start: index, end: index + p1.length + 1 }) }); console.log(result);

Victor P · Accepted Answer · 2019-08-16 14:48:42Z

indexOf only returns the first occurrence of a pattern in a string (see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/indexOf). You COULD override it with your own implementation that simply calls indexOf multiple times and stores the results in an array which it returns as its final result but this would be a bad idea as you'd be overriding the default implementation. A better approach would be to create a new prototype function (eg, String.prototype.indexOfMany).

Community · Accepted Answer · 2020-06-20 09:12:55Z

I would go for String.prototype.match. (Documentation)

It returns all substrings that match a given regex.

For your example you might use something like this:

var stringUnderTest = "/accounts/{account}/project/{project}"; var foundStrings = stringUnderTest.match(/\{[a-z]*\}/gi); console.log(foundStrings);

This way you get all occurences of {...} whose positions you could then determine with indexOf.

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