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

Consider using let or const instead of var JS-0239

Anti-pattern

Major

9 months ago — 3 years old

Unexpected var, use let or const instead

1299    
1300    const raw_json_id = "fireSeqSearchWordcloudRawJson";
1301    var raw_dom = document.getElementById(raw_json_id);
1302    var raw_json = raw_dom.textContent;1303
1304    raw_dom.setAttribute("style", "width: 1000px");
1305    // consoleLogForDebug(raw_json);

Unexpected var, use let or const instead

fireSeqSearch_addon/wordcloud_draw.js

1298    consoleLogForDebug(WordCloud.isSupported);
1299    
1300    const raw_json_id = "fireSeqSearchWordcloudRawJson";
1301    var raw_dom = document.getElementById(raw_json_id);1302    var raw_json = raw_dom.textContent;
1303
1304    raw_dom.setAttribute("style", "width: 1000px");

Unexpected var, use let or const instead

fireSeqSearch_addon/wordcloud_draw.js

1256
1257function process_word_list(word_list, _serverInfo) {
1258    var min_freq = -1;
1259    var max_freq = 1;1260    const max_size = 60;
1261    const min_size = 30;
1262

Unexpected var, use let or const instead

fireSeqSearch_addon/wordcloud_draw.js

1255
1256
1257function process_word_list(word_list, _serverInfo) {
1258    var min_freq = -1;1259    var max_freq = 1;
1260    const max_size = 60;
1261    const min_size = 30;

Unexpected var, use let or const instead

fireSeqSearch_addon/wordcloud_draw.js

1227    WordCloud.minFontSize = minFontSize
1228    WordCloud.stop = function stop () {
1229        if (timer) {
1230            for (var timerId in timer) {1231                window.clearImmediate(timer[timerId])
1232            }
1233        }

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 = {};

Endle / fireSeqSearch

Bad Practice

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