It’s rare that I’m disappointed by the JavaScript language not having a function that I need. One such case was summing an array of numbers — I was expecting Math.sum or a likewise, baked in API. Fear not — summing an array of numbers is easy using Array.prototype.reduce!
const numbers = [1, 2, 3, 4]; const sum = numbers.reduce((a, b) => a + b, 0);
The 0 represents the starting value while with a and b, one represents the running total with the other representing the value to be added. You’ll also note that using reduce prevents side effects! I’d still prefer something like Math.sum(...numbers) but a simple reduce will do!
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Many times you’ll see a form dynamically change available values based on the value of a form field. For example, a “State” field will change based on which Country a user selects. What annoys me about these forms is that they’ll often do an…