This article was co-authored by How.com.vn staff writer, Darlene Antonelli, MA. Darlene Antonelli is a Technology Writer and Editor for How.com.vn. Darlene has experience teaching college courses, writing technology-related articles, and working hands-on in the technology field. She earned an MA in Writing from Rowan University in 2012 and wrote her thesis on online communities and the personalities curated in such communities.
This How.com.vn will teach you how to use the try/catch code in Javascript. "Try" stands for the code you want to attempt to complete while "catch" is the code that runs through if there is an error found. For example, the "catch" could be showing "Username cannot contain special characters (!?*)" when a user tries to enter special characters into the username field.
Steps
Open a JavaScript editor. Notepad and TextEdit are for the default text-editing softwares on Windows and Mac, but you can use software like Visual Studio, if you have it.- To open Notepad on Windows, press the Windows key, type in "Notepad," and click the text editor search result.
- To open TextEdit on Mac, click the magnifying glass icon, type "TextEdit" and click the text editor search result.
Create an HTML document. Add the following code to your document:<!DOCTYPE html><html><body></body></html>
Enter the following example code between the open (<body>) and closed (</body>) tags: the following example code is from https://www.w3schools.com/jsref/jsref_try_catch.asp.<p>Please input a number between 5 and 10:</p><input id="demo" type="text"><button type="button" onclick="myFunction()">Test Input</button><p id="message"></p><script>function myFunction() { var message, x; message = document.getElementById("message"); message.innerHTML = ""; x = document.getElementById("demo").value; try { if(x == "") throw "is Empty"; if(isNaN(x)) throw "not a number"; if(x > 10) throw "too high"; if(x < 5) throw "too low"; } catch(err) {message.innerHTML = "Input " + err; }}</script>
- In this example, the website is asking the user to enter a number 5-10. The "try" code is set to output specific variables depending on the input (Is there an entered variable? Is the entered variable a number? Is it greater than 10? Is it less than 5?) whereas the "catch" code is set to return the user with an error response if none of the conditions in the "try" code are met.
- Save this document as an HTML file and you'll be able to see it in your browser. Go to File > Save As and change the file type to HTML in the drop-down box next to "Save as type." Right-click the file then select Open with > Chrome (or whatever web browser you want to use) and that code should run in your browser.
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Expert Q&A
About this article
1. Open a JavaScript editor.
2. Create an HTML document.
3. Enter the following example code between the open and closed tags.
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