gsap-utils

# gsap.utils ## When to Use This Skill Apply when writing or reviewing code that uses **gsap.utils** for math, array/collection handling, unit parsing, or value mapping in animations (e.g. mapping scroll to a value, randomizing, snapping to a grid, or normalizing inputs). **Related skills:** Use with **gsap-core**, **gsap-timeline**, and **gsap-scrolltrigger** when building animations; CustomEase and other easing utilities are in **gsap-plugins**. ## Overview **gsap.utils** provides pure helpers; no need to register. Use in tween vars (e.g. function-based values), in ScrollTrigger or Observer callbacks, or in any JS that drives GSAP. All are on **gsap.utils** (e.g. `gsap.utils.clamp()`). **Omitting the value: function form.** Many utils accept the value to transform as the **last** argument. If you omit that argument, the util returns a **function** that accepts the value later. Use the function form when you need to clamp, map, normalize, or snap many values with the same config (e.g. in a mousemove handler or tween callback). **Exception: random()** — pass **true** as the last argument to get a reusable function (do not omit the value); see [random()](https://gsap.com/docs/v3/GSAP/UtilityMethods/random()). ```javascript // With value: returns the result gsap.utils.clamp(0, 100, 150); // 100 // Without value: returns a function you call with the value later let c = gsap.utils.clamp(0, 100); c(150); // 100 c(-10); // 0 ``` ## Clamping and Ranges ### clamp(min, max, value?) Constrains a value between min and max. Omit **value** to get a function: `clamp(min, max)(value)`. ```javascript gsap.utils.clamp(0, 100, 150); // 100 gsap.utils.clamp(0, 100, -10); // 0 let clampFn = gsap.utils.clamp(0, 100); clampFn(150); // 100 ``` ### mapRange(inMin, inMax, outMin, outMax, value?) Maps a value from one range to another. Use when converting scroll position, progress (0–1), or input range to an animation range. Omit **value** to get a function: `mapRange(inMin, inMax, outMin, outMax)(value)`. ```javascript gsap.utils.mapRange(0, 100, 0, 500, 50); // 250 gsap.utils.mapRange(0, 1, 0, 360, 0.5); // 180 (progress to degrees) let mapFn = gsap.utils.mapRange(0, 100, 0, 500); mapFn(50); // 250 ``` ### normalize(min, max, value?) Returns a value normalized to 0–1 for the given range. Inverse of mapping when the target range is 0–1. Omit **value** to get a function: `normalize(min, max)(value)`. ```javascript gsap.utils.normalize(0, 100, 50); // 0.5 gsap.utils.normalize(100, 300, 200); // 0.5 let normFn = gsap.utils.normalize(0, 100); normFn(50); // 0.5 ``` ### interpolate(start, end, progress?) Interpolates between two values at a given progress (0–1). Handles numbers, colors, and objects with matching keys. Omit **progress** to get a function: `interpolate(start, end)(progress)`. ```javascript gsap.utils.interpolate(0, 100, 0.5); // 50 gsap.utils.interpolate("#ff0000", "#0000ff", 0.5); // mid color gsap.utils.interpolate({ x: 0, y: 0 }, { x: 100, y: 50 }, 0.5); // { x: 50, y: 25 } let lerp = gsap.utils.interpolate(0, 100); lerp(0.5); // 50 ``` ## Random and Snap ### random(minimum, maximum[, snapIncrement, returnFunction]) / random(array[, returnFunction]) Returns a random number in the range **minimum**–**maximum**, or a random element from an **array**. Optional **snapIncrement** snaps the result to the nearest multiple (e.g. `5` → multiples of 5). **To get a reusable function**, pass **true** as the last argument (**returnFunction**); the returned function takes no args and returns a new random value each time. This is the only util that uses `true` for the function form instead of omitting the value. ```javascript // immediate value: number in range gsap.utils.random(-100, 100); // e.g. 42.7 gsap.utils.random(0, 500, 5); // 0–500, snapped to nearest 5 // reusable function: pass true as last argument let randomFn = gsap.utils.random(-200, 500, 10, true); randomFn(); // random value in range, snapped to 10 randomFn(); // another random value // array: pick one value at random gsap.utils.random(["red", "blue", "green"]); // "red", "blue", or "green" let randomFromArray = gsap.utils.random([0, 100, 200], true); randomFromArray(); // 0, 100, or 200 ``` **String form in tween vars:** use `"random(-100, 100)"`, `"random(-100, 100, 5)"`, or `"random([0, 100, 200])"`; GSAP evaluates it per target. ```javascript gsap.to(".box", { x: "random(-100, 100, 5)", duration: 1 }); gsap.to(".item", { backgroundColor: "random([red, blue, green])" }); ``` ### snap(snapTo, value?) Snaps a value to the nearest multiple of **snapTo**, or to the nearest value in an array of allowed values. Omit **value** to get a function: `snap(snapTo)(value)` (or `snap(snapArray)(value)`). ```javascript gsap.utils.snap(10, 23); // 20 gsap.utils.snap(0.25, 0.7); // 0.75 gsap.utils.snap([0, 100, 200], 150); // 100 or 200 (nearest in array) let snapFn = gsap.utils.snap(10); snapFn(23); // 20 ``` Use in tweens for grid or step-based animation: ```javascript gsap.to(".x", { x: 200, snap: { x: 20 } }); ``` ### shuffle(array) Returns a new array with the same elements in random order. Use for randomizing order (e.g. stagger from "random" with a copy). ```javascript gsap.utils.shuffle([1, 2, 3, 4]); // e.g. [3, 1, 4, 2] ``` ### distribute(config) **Returns a function** that assigns a value to each target based on its position in the array (or in a grid). Used internally for advanced staggers; use it whenever you need values spread across many elements (e.g. scale, opacity, x, delay). The returned function receives `(index, target, targets)` — either call it manually or pass the result directly into a tween; GSAP will call it per target with index, element, and array. **Config (all optional):** | Property | Type | Description | |----------|------|-------------| | `base` | Number | Starting value. Default `0`. | | `amount` | Number | Total to distribute across all targets (added to base). E.g. `amount: 1` with 100 targets → 0.01 between each. Use **each** instead to set a fixed step per target. | | `each` | Number | Amount to add between each target (added to base). E.g. `each: 1` with 4 targets → 0, 1, 2, 3. Use **amount** instead to split a total. | | `from` | Number \| String \| Array | Where distribution starts: index, or `"start"`, `"center"`, `"edges"`, `"random"`, `"end"`, or ratios like `[0.25, 0.75]`. Default `0`. | | `grid` | String \| Array | Use grid position instead of flat index: `[rows, columns]` (e.g. `[5, 10]`) or `"auto"` to detect. Omit for flat array. | | `axis` | String | For grid: limit to one axis (`"x"` or `"y"`). | | `ease` | Ease | Distribute values along an ease curve (e.g. `"power1.inOut"`). Default `"none"`. | **In a tween:** pass the result of `distribute(config)` as the property value; GSAP calls the function for each target with `(index, target, targets)`. ```javascript // Scale: middle elements 0.5, outer edges 3 (amount 2.5 distributed from center) gsap.to(".class", { scale: gsap.utils.distribute({ base: 0.5, amount: 2.5, from: "center" }) }); ``` **Manual use:** call the returned function with `(index, target, targets)` to get the value for that index. ```javascript const distributor = gsap.utils.distribute({ base: 50, amount: 100, from: "center", ease: "power1.inOut" }); const targets = gsap.utils.toArray(".box"); const valueForIndex2 = distributor(2, targets[2], targets); ``` See [distribute()](https://gsap.com/docs/v3/GSAP/UtilityMethods/distribute/) for more. ## Units and Parsing ### getUnit(value) Returns the unit string of a value (e.g. `"px"`, `"%"`, `"deg"`). Use when normalizing or converting values. ```javascript gsap.utils.getUnit("100px"); // "px" gsap.utils.getUnit("50%"); // "%" gsap.utils.getUnit(42); // "" (unitless) ``` ### unitize(value, unit) Appends a unit to a number, or returns the value as-is if it already has a unit. Use when building CSS values or tween end values. ```javascript gsap.utils.unitize(100, "px"); // "100px" gsap.utils.unitize("2rem", "px"); // "2rem" (unchanged) ``` ### splitColor(color, returnHSL?) Converts a color string into an array: **[red, green, blue]** (0–255), or **[red, green, blue, alpha]** (4 elements for RGBA when alpha is present or required). Pass **true** as the second argument (**returnHSL**) to get **[hue, saturation, lightness]** or **[hue, saturation, lightness, alpha]** (HSL/HSLA) instead. Works with `"rgb()"`, `"rgba()"`, `"hsl()"`, `"hsla()"`, hex, and named colors (e.g. `"red"`). Use when animating color components or building gradients. See [splitColor()](https://gsap.com/docs/v3/GSAP/UtilityMethods/splitColor/). ```javascript gsap.utils.splitColor("red"); // [255, 0, 0] gsap.utils.splitColor("#6fb936"); // [111, 185, 54] gsap.utils.splitColor("rgba(204, 153, 51, 0.5)"); // [204, 153, 51, 0.5] (4 elements) gsap.utils.splitColor("#6fb936", true); // [94, 55, 47] (HSL: hue, saturation, lightness) ``` ## Arrays and Collections ### selector(scope) Returns a scoped selector function that finds elements only within the given element (or ref). Use in components so selectors like `".box"` match only descendants of that component, not the whole document. Accepts a DOM element or a ref (e.g. React ref; handles `.current`). ```javascript const q = gsap.utils.selector(containerRef); q(".box"); // array of .box elements inside container gsap.to(q(".circle"), { x: 100 }); ``` ### toArray(value, scope?) Converts a value to an array: selector string (scoped to element), NodeList, HTMLCollection, single element, or array. Use when passing mixed inputs to GSAP (e.g. targets) and a true array is needed. ```javascript gsap.utils.toArray(".item"); // array of elements gsap.utils.toArray(".item", container); // scoped to container gsap.utils.toArray(nodeList); // [ ... ] from NodeList ``` ### pipe(...functions) Composes functions: **pipe(f1, f2, f3)(value)** returns f3(f2(f1(value))). Use when applying a chain of transforms (e.g. normalize → mapRange → snap) in a tween or callback. ```javascript const fn = gsap.utils.pipe( (v) => gsap.utils.normalize(0, 100, v), (v) => gsap.utils.snap(0.1, v) ); fn(50); // normalized then snapped ``` ### wrap(min, max, value?)