diff options
Diffstat (limited to 'deps/npm/node_modules/asap/browser-asap.js')
-rw-r--r-- | deps/npm/node_modules/asap/browser-asap.js | 66 |
1 files changed, 66 insertions, 0 deletions
diff --git a/deps/npm/node_modules/asap/browser-asap.js b/deps/npm/node_modules/asap/browser-asap.js new file mode 100644 index 00000000000..805c9824605 --- /dev/null +++ b/deps/npm/node_modules/asap/browser-asap.js @@ -0,0 +1,66 @@ +"use strict"; + +// rawAsap provides everything we need except exception management. +var rawAsap = require("./raw"); +// RawTasks are recycled to reduce GC churn. +var freeTasks = []; +// We queue errors to ensure they are thrown in right order (FIFO). +// Array-as-queue is good enough here, since we are just dealing with exceptions. +var pendingErrors = []; +var requestErrorThrow = rawAsap.makeRequestCallFromTimer(throwFirstError); + +function throwFirstError() { + if (pendingErrors.length) { + throw pendingErrors.shift(); + } +} + +/** + * Calls a task as soon as possible after returning, in its own event, with priority + * over other events like animation, reflow, and repaint. An error thrown from an + * event will not interrupt, nor even substantially slow down the processing of + * other events, but will be rather postponed to a lower priority event. + * @param {{call}} task A callable object, typically a function that takes no + * arguments. + */ +module.exports = asap; +function asap(task) { + var rawTask; + if (freeTasks.length) { + rawTask = freeTasks.pop(); + } else { + rawTask = new RawTask(); + } + rawTask.task = task; + rawAsap(rawTask); +} + +// We wrap tasks with recyclable task objects. A task object implements +// `call`, just like a function. +function RawTask() { + this.task = null; +} + +// The sole purpose of wrapping the task is to catch the exception and recycle +// the task object after its single use. +RawTask.prototype.call = function () { + try { + this.task.call(); + } catch (error) { + if (asap.onerror) { + // This hook exists purely for testing purposes. + // Its name will be periodically randomized to break any code that + // depends on its existence. + asap.onerror(error); + } else { + // In a web browser, exceptions are not fatal. However, to avoid + // slowing down the queue of pending tasks, we rethrow the error in a + // lower priority turn. + pendingErrors.push(error); + requestErrorThrow(); + } + } finally { + this.task = null; + freeTasks[freeTasks.length] = this; + } +}; |