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for...of vs for...in: Which Loop for Which Job

for...of gives you the values of an array. for...in gives you the keys of an object, as strings. Mix them up and you get indexes instead of items, or worse.

4 min read
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Fix a Const Assignment Error in a Browser Filter

Trace a const reassignment inside an input handler, preserve the original list, and verify that filtering and clearing the query both work.

5 min read
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Template Literals: Stop Gluing Strings With +

Backticks and ${} replace most string gluing with +. You get readable text, values inside it, and multi-line strings without \n everywhere.

3 min read
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Why "5" + 1 Is "51": Type Conversion in JavaScript

"5" + 1 is "51" because + joins text before it adds numbers. Convert values on purpose with Number(), String() and parseInt(), check for NaN, and stop letting JavaScript guess for you.

4 min read