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A JavaScript library that provides a convenient way to create CSS transitions pragmatically.

  • Correctly cleans and restarts CSS transition properties while calling their onTransitionEnd callbacks.
  • Correctly adds new transitions to an element with already running transitions.
  • Provides the onTransitionEnd callback that is called not only when the transition was finished, but also when the transition was halted. For example, when a transition was manually stopped (not yet implemented) or another transition with the same transition property started on the same element.
  • All transitions scheduled in the same JavaScript execution context stack will be started together and in a separate execution context stack.
  • Supports AMD and Global scope inclusion.

Visit for more info and examples.

Basic Usage

Following code fades out an element by transitioning its opacity from 1 to 0 and its scale from 1 to 0.5. Both properties transitioned with a duration of 400 milliseconds. After transition finishes, the element's display is set to none.

transition.begin(element, [
        "opacity 1 0",
        "transform scale(1) scale(0.5)"
    ], {
        // Duration of 400ms is used both for opacity and transform
        duration: "400ms",
        onTransitionEnd: function(element, finished) {
            // if transition will be halted in the middle, finished will equal to false
            if (finished) {
                // If the transition was finished naturally, hide the element.
       = "none";


transition.begin(element, properties[, options])

The begin method applies CSS transition effect on the passed element using the passed properties that define the transition effect.


element - The element on which the CSS transition effect will be applied.

properties - The transition properties of a single or multiple CSS transitions. This parameter can take several forms:

  • Array: [propertyName, fromValue, toValue[, duration, timingFunction, delay, onTransitionEnd]]
    example: ["opacity", "0", "1", "1s", "linear", "0s", onTransitionEndCallback]
    Array of transition properties and transition values. The first three values are required and must be specified in the following order: a CSS transition property name, a value to transition "from" and a value to transition "to". The rest of the values (duration, delay, timing function and onTransitionEnd callback) are optional and their order conforms to the CSS transition property specification: the first value that can be parsed as a time is assigned to the transition-duration, and the second value that can be parsed as a time is assigned to transition-delay.
  • String: `${propertyName} ${fromValue} ${toValue}[ ${duration} ${timingFunction} ${delay}]`
    Example: "opacity 0 1 1s linear 0s"
    String with space separated transition properties and transition values. The order and the requirements of the values in this string must follow the same rules defined for the values specified inside an array. Due to its nature, this form does not allow specifying the onTransitionEnd callback.
    Note: some CSS properties (e.g.: transform) can themselves receive a space separated values such as transform: translateX(200px) rotate(180deg);. In this case, you should use the "Array" form.
  • Object: {property: "opacity", from: "0", to: "1"}
    Using this form, you can specify all the properties you can specify using the array form (property name, from value, to value, duration, delay, timingFunction and onTransitionEnd callback). In addition, you can specify the beginFromCurrentValue flag. Visit for more info and examples.
  • Array of Arrays, Strings or Objects
    Array of Arrays, Strings or Objects, each specifying single transition property. This form allows transitioning multiple transition properties on a single element at once:
    ["opacity 0 1 1s", ["color", "red", "blue", "500ms"]]

options - Transition options object with the following optional fields:

  • onTransitionEnd
    A callback function that is called when all transition properties have finished their transitions. Receives two parameters, element and finished. The finished parameter will be false if the transition was stopped or one of the transitioned properties was used in a new transition.
  • onBeforeChangeStyle
    A callback function that is called before the new CSS property value is applied to the element. This callback tries to mimic the before-change style event.
  • onAfterChangeStyle
    A callback function that is called after the new CSS property value is applied to the element. This callback tries to mimic the after-change style event.
  • beginFromCurrentValue
    Sets the default beginFromCurrentValue value for properties that do not specify their own beginFromCurrentValue value. See examples below for more info.
  • duration
    Sets the default transition-duration for the transition properties that do not specify their own duration. Default is 400ms.
  • delay
    Sets the default transition-delay for the transition properties that do not specify their own delay. Default is 0s.
  • timingFunction
    Sets the default transition-timing-function for the transition properties that do not specify their own timing-function. Default is ease.


An object with a promise field holding a Promise that will be resolved when the transition ends. In a similar way to the onFulfilled callback, the promise resolves with an object having two fields: the animated element and the finished flag that indicating if the transition finished animating.

transition.begin(element, "opacity 1 0 2s").promise.then(function(result) {
    // result.element - the animated element
    // result.finished - is the transition finished animating or was halted in the middle

Advanced Usage Example

function fadeOut(element) {
    // Don't let fade out transition to finish, begin fading-in again in the middle of fade-out transition.
    window.setTimeout(function() {
    }, 1000);
    transition.begin(element, "opacity 1 0 2s", {
        onTransitionEnd: function(element, finished) {
            // Because we called fadeIn from within setTimeout with 1s, the fade-in transition will be halted
            // in the middle and this callback will be invoked with finished set to "false".
            if (finished) {
                // This code never runs, because finished is false

function fadeIn(element) {
    transition.begin(element, "opacity 0 1 2s", {
        // On successive runs, fadeIn is called from within setTimeout function while fade-out transition is running.
        // Setting beginFromCurrentValue to true makes sure the new fade-in transition will continue the effect from
        // the current opacity calue and not 0.
        beginFromCurrentValue: true,
        onBeforeChangeStyle: function(element) {
            // When fading-in for the first time, add the element to the DOM right after the
            // opacity is set to 0 but before transition properties are applied on the element. 
            if (!element.parentNode) {
        onTransitionEnd: function(element, finished) {
            // Fade out the element right after it had finished fading in.

var element = document.createElement("div"); = "position: absolute; top: 100px; left:100px; width: 100px; height: 100px; background: #ff0000";


A JavaScript library that provides a convenient way to create CSS transitions pragmatically




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