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The setInterval() method calls a function at specified intervals (in milliseconds). The setInterval() method continues calling the function until clearInterval() is called, or the window is closed. 1 second = 1000 milliseconds.
- Js Timing
The two key methods to use with JavaScript are:...
- Js Timing
Jun 3, 2024 · setInterval() is for executing a function repeatedly at specified intervals until explicitly cleared. Syntax: setInterval(function, delay); function: The function to be executed at each interval. delay: The time, in milliseconds, between each execution of the function. Return Value: Returns a Number which is basically the id of the timer.
- Overview
- Syntax
- Examples
- The "this" problem
- Usage notes
- Browser compatibility
- See also
The setInterval() method, offered on the Window and WorkerGlobalScope interfaces, repeatedly calls a function or executes a code snippet, with a fixed time delay between each call.
This method returns an interval ID which uniquely identifies the interval, so you can remove it later by calling clearInterval().
Parameters
func A function to be executed every delay milliseconds. The first execution happens after delay milliseconds. code An optional syntax allows you to include a string instead of a function, which is compiled and executed every delay milliseconds. This syntax is not recommended for the same reasons that make using eval() a security risk. delay Optional The time, in milliseconds (thousandths of a second), the timer should delay in between executions of the specified function or code. Defaults to 0 if not specified. See Delay restrictions below for details on the permitted range of delay values. arg1, …,argN Optional Additional arguments which are passed through to the function specified by func once the timer expires.
Return value
The returned intervalID is a numeric, non-zero value which identifies the timer created by the call to setInterval(); this value can be passed to clearInterval() to cancel the interval. It may be helpful to be aware that setInterval() and setTimeout() share the same pool of IDs, and that clearInterval() and clearTimeout() can technically be used interchangeably. For clarity, however, you should try to always match them to avoid confusion when maintaining your code.
Example 1: Basic syntax
The following example demonstrates setInterval()'s basic syntax.
Example 2: Alternating two colors
The following example calls the flashtext() function once a second until the Stop button is pressed.
Explanation
Code executed by setInterval() runs in a separate execution context than the function from which it was called. As a consequence, the this keyword for the called function is set to the window (or global) object, it is not the same as the this value for the function that called setTimeout. See the following example (which uses setTimeout() instead of setInterval() – the problem, in fact, is the same for both timers): As you can see there are no ways to pass the this object to the callback function in the legacy JavaScript.
A possible solution
All modern JavaScript runtimes (in browsers and elsewhere) support arrow functions, with lexical this — allowing us to write setInterval(() => this.myMethod()) if we're inside the myArray method. If you need to support IE, use the Function.prototype.bind() method, which lets you specify the value that should be used as this for all calls to a given function. That lets you easily bypass problems where it's unclear what this will be, depending on the context from which your function was called.
Delay restrictions
It's possible for intervals to be nested; that is, the callback for setInterval() can in turn call setInterval() to start another interval running, even though the first one is still going. To mitigate the potential impact this can have on performance, once intervals are nested beyond five levels deep, the browser will automatically enforce a 4 ms minimum value for the interval. Attempts to specify a value less than 4 ms in deeply-nested calls to setInterval() will be pinned to 4 ms. Browsers may enforce even more stringent minimum values for the interval under some circumstances, although these should not be common. Note also that the actual amount of time that elapses between calls to the callback may be longer than the given delay; see Reasons for delays longer than specified for examples.
Ensure that execution duration is shorter than interval frequency
If there is a possibility that your logic could take longer to execute than the interval time, it is recommended that you recursively call a named function using setTimeout(). For example, if using setInterval() to poll a remote server every 5 seconds, network latency, an unresponsive server, and a host of other issues could prevent the request from completing in its allotted time. As such, you may find yourself with queued up XHR requests that won't necessarily return in order. In these cases, a recursive setTimeout() pattern is preferred: In the above snippet, a named function loop() is declared and is immediately executed. loop() is recursively called inside setTimeout() after the logic has completed executing. While this pattern does not guarantee execution on a fixed interval, it does guarantee that the previous interval has completed before recursing.
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•Polyfill of setInterval which allows passing arguments to the callback in core-js
•setTimeout()
•clearTimeout()
•clearInterval()
The commonly used syntax of JavaScript setInterval is: setInterval(function, milliseconds); Its parameters are: function - a function containing a block of code; milliseconds - the time interval between the execution of the function; The setInterval() method returns an intervalID which is a positive integer.
The two key methods to use with JavaScript are: setTimeout(function, milliseconds) Executes a function, after waiting a specified number of milliseconds. setInterval(function, milliseconds) Same as setTimeout (), but repeats the execution of the function continuously.
Mar 17, 2021 · The JavaScript setInterval() method is a method from the DOM Window object that allows you to run a specific function at a defined interval. For example, the following fnLog() function will be executed every 1 second: let timer = setInterval(fnLog, 1000); function fnLog() { console.log("Function fnLog executed"); }
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In this tutorial, you will learn how to use the JavaScript setInterval() to repeatedly call a function with a fixed delay between each call.
