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This post is part of my Today I learned series in which I share all my web development learnings.

Rodney Rehm recently tweeted about this function I have never heard of – String.prototype.localCompare. And wow - this can be so useful.

  • Did you want to know if a string includes a given character sequence no matter if upper or lower case?
  • Did you ever come across the problem that when you want to compare strings that include numeric values that this is usually not so easy?
'aBcD' === 'abcd' // false
'ábcd' === 'abcd' // false

'Price 2€'  > 'Price 1€'  // true
'Price 20€' > 'Price 3€' // false

Using localCompare you can define several options that can help out here. According to MDN it returns the following value:

A negative number if the reference string occurs before the compare string; positive if the reference string occurs after the compare string; 0 if they are equivalent.

So let's have a look

'aBcD'.localeCompare('abcd', undefined, { sensitivity: 'base' }) // 0 -> equal
'ábcd'.localeCompare('abcd', undefined, { sensitivity: 'base' }) // 0 -> equal

'Price 20€'.localeCompare('Price 3€', undefined, { numeric: true })  // 1
'Price 20€'.localeCompare('Price 3€', undefined, { numeric: false }) // -1

This can help to find out if strings have an equal base without fiddling around with numeric code point values and you have to admit that the numeric option is really cool!!!

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About Stefan Judis

Frontend nerd with over ten years of experience, freelance dev, "Today I Learned" blogger, conference speaker, and Open Source maintainer.

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