How to read javascript timer

JavaScript is a front-end development language that is widely used in web development. The timer is a very commonly used function. Users can set the timer to achieve some automated operations. In JavaScript, there are two types of timers: setInterval and setTimeout.

setInterval can set a periodic timer so that a piece of code is executed at a certain interval. setTimeout triggers the execution of a piece of code through a certain delay time.

However, for beginners, how to check the execution of JavaScript timer is a problem. The following article will introduce how to view the execution of JavaScript timer.

1. Chrome DevTools

Chrome DevTools is a developer tool that comes with the Chrome browser. It provides a very useful JavaScript debugging tool that can interactively view variables and DOM. Nodes and CSS styles, etc. At the same time, Chrome DevTools also provides the function of debugging JavaScript timers.

1. Open Chrome DevTools

First, you need to open the Chrome browser and find the page you want to debug. Then, open Chrome DevTools by pressing the F12 key on your keyboard or selecting "Inspect" from the right-click menu.

2. Select the "Console" panel

After opening Chrome DevTools, you need to select the "Console" panel. The console panel provides an interactive terminal for JavaScript, where you can enter commands to debug JavaScript code.

3. Enter the monitoring command

Next, you need to enter the monitoring command. You can enter the following command to monitor timers:

• setInterval: monitor all periodic timers
• setTimeout: monitor all delay timers

For example, you can enter the following command to monitor a periodic timer:

setInterval(function() { console.log("Hello, world!"); }, 1000)

This will output a "Hello, world!" to the console every 1 second.

4. View monitoring results

After you enter the monitoring command, you can see the output results in the console. For periodic timers, you can see that they fire every once in a while, and for delay timers, you can see that they fire after a certain amount of time.

2. Firebug plug-in

Firebug is a Firefox browser plug-in that provides debugging functions similar to Chrome DevTools. With the Firebug plugin, you can easily monitor the execution of JavaScript timers.

1. Install the Firebug plug-in

First, you need to install the Firebug plug-in in the Firefox browser. You can install it by searching for "Firebug" in the Firefox add-on store.

2. Open Firebug

After the installation is complete, you need to open the Firebug plug-in. You can find an icon called "Firebug" on the Firefox toolbar. Click it to open Firebug.

3. Select the "Console" panel

After opening Firebug, you need to select the "Console" panel. The console panel provides an interactive terminal for JavaScript, where you can enter commands to debug JavaScript code.

4. Enter the watch command

Similarly, you need to enter the watch command to monitor the timer. You can enter the following command to monitor the periodic timer:

setInterval(function() { console.log("Hello, world!"); }, 1000)

5. View monitoring results

After entering the monitoring command, you can see the output results in the console. For periodic timers, you can see that they fire every once in a while, and for delay timers, you can see that they fire after a certain amount of time.

Summary

It is very useful to monitor the execution of JavaScript timers. By monitoring timers, you can better understand the execution logic of your code and identify problems. This article describes how to monitor the execution of JavaScript timers through Chrome DevTools and Firebug plug-ins. I believe this will be helpful for your JavaScript development work.

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