JS-0239 · Consider using `let` or `const` instead of `var`

Consider using let or const instead of var JS-0239

Anti-pattern

Major

15 days ago — 3 years old

Unexpected var, use let or const instead

 68                return this.components ? this.selected.length == this.components.length : false;
 69            },
 70            set: function(value) {
 71                var selected = []; 72
 73                if (value) {
 74                    this.components.forEach(function(component) {

Unexpected var, use let or const instead

src/componentAPI.ts

 57import NormallyClosedValveModificationsGap from "./app/library/geometricElements/normallyClosedValveGap";
 58import { ValveType } from "./app/core/init";
 59
 60export var PRIMITIVES_SERVER = false; 61
 62export function enablePrimitiveServer() {
 63    PRIMITIVES_SERVER = true;

Unexpected var, use let or const instead

src/assets/lib/nouislider/nouislider.js

2236        target.noUiSlider = api;
2237        return api;
2238    }
2239    var nouislider = {2240        // Exposed for unit testing, don't use this in your application.2241        __spectrum: Spectrum,2242        // A reference to the default classes, allows global changes.2243        // Use the cssClasses option for changes to one slider.2244        cssClasses: cssClasses,2245        create: initialize,2246    };2247
2248    exports.create = initialize;
2249    exports.cssClasses = cssClasses;

Unexpected var, use let or const instead

src/assets/lib/nouislider/nouislider.js

2232        }
2233        // Test the options and create the slider environment;
2234        var options = testOptions(originalOptions);
2235        var api = scope(target, options, originalOptions);2236        target.noUiSlider = api;
2237        return api;
2238    }

Unexpected var, use let or const instead

src/assets/lib/nouislider/nouislider.js

2231            throw new Error("noUiSlider: Slider was already initialized.");
2232        }
2233        // Test the options and create the slider environment;
2234        var options = testOptions(originalOptions);2235        var api = scope(target, options, originalOptions);
2236        target.noUiSlider = api;
2237        return api;

Description

It is recommended to use let or const over var. This will help prevent re-declaration of variables that are in the global scope when using var.

ES6 allows programmers to create variables with block scope instead of function scope using the let and const keywords. Block scope is common in many other programming languages and helps programmers avoid mistakes such as this one:

var count = people.length;
var enoughFood = count > sandwiches.length;

if (enoughFood) {
    var count = sandwiches.length; // accidentally overriding the count variable
    console.log("We have " + count + " sandwiches for everyone. Plenty for all!");
}

// our count variable is no longer accurate
console.log("We have " + count + " people and " + sandwiches.length + " sandwiches!");

Block scoped variables shadow outer declarations instead of writing to them.

NOTE: There are certain edge cases where users might want to consider var. Consider this example:

var lib = lib || { run: () => {} }

Here, lib might be a library that is exposed to an HTML file using a <script> tag. The var keyword helps avoid re-writing lib if it has already been declared via an injected script that was executed before this one. Ideally, you should let bundlers worry about cases like this. But if you want to use var anyway, consider using a skipcq comment, or disabling the issue altogether.

Bad Practice

var x = "y";
var CONFIG = {};

CIDARLAB / 3DuF

Bad Practice

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