


jQuery usage practice: several ways to determine whether a variable is empty
Feb 27, 2024 pm 04:12 PMjQuery is a JavaScript library widely used in web development. It provides many simple and convenient methods to operate web page elements and handle events. In actual development, we often encounter situations where we need to determine whether a variable is empty. This article will introduce several common methods of using jQuery to determine whether a variable is empty, and attach specific code examples.
Method 1: Use the if statement to determine
var str = ""; if (str) { console.log("變量不為空"); } else { console.log("變量為空"); }
Method 2: Use the length attribute to determine
var arr = []; if (arr.length > 0) { console.log("變量不為空"); } else { console.log("變量為空"); }
Method 3: Use jQuery’s isEmptyObject method to determine
var obj = {}; if (!$.isEmptyObject(obj)) { console.log("變量不為空"); } else { console.log("變量為空"); }
Method 4: Use the $.trim method to determine whether the string is a space
var str = " "; if ($.trim(str).length > 0) { console.log("變量不為空"); } else { console.log("變量為空"); }
Method 5: Use !== to determine whether the variable is undefined or null
var variable; if (variable !== undefined && variable !== null) { console.log("變量不為空"); } else { console.log("變量為空"); }
The above are several commonly used judgment variables In actual development, you can choose an appropriate method to determine whether a variable is empty according to specific needs. Through reasonable judgment, you can avoid errors when the program is running and improve the robustness and reliability of the code. I hope this article can help readers in need. Welcome to communicate and share more tips on using jQuery.
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