What does ::: mean in javascript

Question

I'm reading a js file for transforming of one spatial model(.gml). from a specific projection to another. What does ":::" mean in the code as follows?

_getTransformation(projectionFrom, projectionTo) {
    let cacheKey = `${projectionFrom}:::${projectionTo}`;
    if (!this.transformations[cacheKey]) {
      let from = this._getProjection(projectionFrom);
      let to = this._getProjection(projectionTo);
      this.transformations[cacheKey] = proj4(from, to);
    }
    return this.transformations[cacheKey];
}

That is just a string. Pretty much like - `projectionFrom + ":::" + projectionTo` — Eddie, Aug 14 '19 at 02:52
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Template_literals — Eddie, Aug 14 '19 at 02:52
Thank you for answering my first question in stack overflow~ — Bayernzc, Aug 14 '19 at 03:00

score 2 · Accepted Answer · edited Aug 14 '19 at 03:48

2

The string with ` is called a template literal, it's an ES6 string making multiple lines and interpolation easier. The ::: is just a collection of three characters in the string. It's equivalent to:

let cacheKey = projectionFrom + ":::" + projectionTo;

No special characters involved bar the ${} - that signifies that the contents should be treated like an expression, the result of which is inserted into the string.

edited Aug 14 '19 at 03:48

gman

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answered Aug 14 '19 at 02:54

Jack Bashford

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No worries @Bayernzc, always glad to help. If my answer fixed your problem, please mark it as accepted by clicking the grey tick mark to the left of my answer. – Jack Bashford Aug 14 '19 at 03:34

What does ::: mean in javascript

1 Answers1