Super simple cancellation token

cancel-token.js

/**
 * A super simple cancel token utility, with support all the way to ES3. Works
 * in browsers, AMD, and CommonJS environments. 874 bytes minified and gzipped.
 *
 * The API is pretty simple:
 *
 * `const source = cancelSource(parentTokens?)`
 *
 * - `source.cancel(reason?)`
 *   Trigger a cancel with some reason, and save the cancel result to
 *   potentially rethrow.
 *
 * - `source.close()`
 *   Close the token without canceling
 *
 * - `const token = source.token`
 *   A reference to the corresponding token for the source
 *
 * - `const tok = source.token.listen(callback)`
 *   Register a callback to be called if/when the token is canceled, with
 *   the cancel instance (if canceled) or `undefined` (if closed)
 *
 * - `source.token.unlisten(tok)`
 *   Remove a registered callback
 *
 * - `const inst = source.token.canceled()`
 *   Returns the instance if the token was canceled, `undefined` otherwise
 *
 * - `source.token.throwIfCanceled()`
 *   Throw the cancel result if the token was canceled
 *
 * - `inst.type`
 *   Set to `"cancel"`, so it's easy to identify them
 *
 * - `inst.reason`
 *   The reason given when it was first created
 */

/**
 * @license ISC
 *
 * Copyright (c) 2017 and later, Isiah Meadows
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
 * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
 * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
 * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
 * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
 * PERFORMANCE OF THIS SOFTWARE.
 */

;(function (global, cancelSource) {
    "use strict"
    if (typeof module === "object" && module && module.exports) {
        module.exports = cancelSource
    } else if (typeof exports === "object" && exports) {
        exports.cancelSource = cancelSource
    } else if (typeof define === "function" && define.amd) {
        define("cancel-source", function () { return cancelSource })
    } else {
        global.cancelSource = cancelSource
    }
})(
    typeof window === "object" && window ||
    typeof self === "object" && self ||
    this,
function (parents) {
    "use strict"
    var callbacks = [], inst
    function end(cancel) {
        if (callbacks) {
            var list = callbacks
            for (var i = callbacks = 0; i < list.length; i++) {
                (0, list[i].f)(inst = cancel)
            }
        }
    }
    if (parents) for (var i = 0; i < parents.length; i++) parents[i].listen(end)
    return {
        cancel: function (reason) {
            end({type: "cancel", reason: reason})
        },
        close: function () {
            end(/* undefined */)
        },
        token: {
            listen: function (func) {
                callbacks.push(func = {f: func})
                return func
            },
            unlisten: function (func) {
                for (var i = 0; i < callbacks.length; i++) {
                    if (callbacks[i] === func) {
                        callbacks.splice(i, 1)
                        break
                    }
                }
            },
            canceled: function () {
                return inst
            },
            throwIfCanceled: function () {
                if (inst) throw inst
            }
        }
    }
});

cancel-token.min.js

/**
 * @license ISC
 *
 * Copyright (c) 2017 and later, Isiah Meadows
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
 * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
 * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
 * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
 * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
 * PERFORMANCE OF THIS SOFTWARE.
 */
!function(e,n){"use strict";"object"==typeof module&&module&&module.exports?module.exports=n:"object"==typeof exports&&exports?exports.cancelSource=n:"function"==typeof define&&define.amd?define("cancel-source",function(){return n}):e.cancelSource=n}("object"==typeof window&&window||"object"==typeof self&&self||this,function(e){"use strict";function n(e){if(o)for(var n=o,c=o=0;c<n.length;c++)(0,n[c].f)(t=e)}var t,o=[];if(e)for(var c=0;c<e.length;c++)e[c].listen(n);return{cancel:function(e){n({type:"cancel",reason:e})},close:function(){n()},token:{listen:function(e){return o.push(e={f:e}),e},unlisten:function(e){for(var n=0;n<o.length;n++)if(o[n]===e){o.splice(n,1);break}},canceled:function(){return t},throwIfCanceled:function(){if(t)throw t}}}});