Collection of small useful javascript functions

PublishedMay 31, 2017

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Collection of small useful javascript functions

Søren Kruse

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Søren Kruse | .NET, C# and Azure

51 posts

Pad left

This will add a character to the left of the input value until the total length of the value is the specified width.

This is useful for stuff like right-aligning text and padding numbers with leading zeros.

var padLeft = function (value, width, char) { char = (char !== undefined) ? char : " "; width = (typeof width === "number") ? width : parseInt(width); value = String(value); return Array(1 + width - value.length).join(char) + value; }

This works with both strings and numbers for input. Please note that negative numbers is not handled correctly.

Examples

// Right-aligning text padLeft("Blue", 10, " ") padLeft("Orange", 10, " ") // Result: // Blue // Orange

// Padding numbers with leading zeros padLeft(5, 3, 0) padLeft(42, 3, 0) padLeft(137, 3, 0) // Result: // 005 // 042 // 137

Debounce

Debouncing means waiting a set amount of time before executing a specified function.

This is useful in many different situations, for example an autosuggest feature where you only want to load suggestion after the user is done typing instead of continuously after each keypress.

// 'wait' is time in milliseconds var debounce = function (func, wait) { var timeout; return function () { var context = this, args = arguments; clearTimeout(timeout); timeout = setTimeout(function () { func.apply(context, args); }, wait || 0); }; }

Examples

var loadSuggestions = function() { // Load suggestions from web service } // debounce(..) returns a new function. // You have to save and reuse the returned function for it to work as expected. var loadSuggestionsDebounce = debounce(loadSuggestions, 250); var textfield = document.getElementById("textfield"); textfield.addEventListener("keypress", loadSuggestionsDebounce);

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Pad left

Examples

Debounce

Examples