Variable Scope Solution 2: We can use typeofoperatorto check the variable is defined or not. if (typeof variable !== 'undefined') { // the variable is defined } Solution 3: You can use this code: if (typeof var
Determining the sign of a number is super easy now with ES6's Math.sign! It will indicate whether the number is positive, negative or zero...
In the above example, we have used the first if statement to check if the "a" variable is either undefined or null. If it satisfies either of the conditions, then the if block will execute; otherwise, the else block will execute. In the second statement, we have used the if statement ...
Here's a Code Recipe to check whether a variable or value is either an array or not. You can use the Array.isArray() method. For older browser, you can use the polyfill 👍 constvariable=['🍝','🍜','🍲'];// ✅ NEWER BROWSERArray.isArray(variable);// 🕰 OLDER BROWSERObj...
If you put a number in quotes, it will be treated as a text string. Example constpi =3.14; letperson ="John Doe"; letanswer ='Yes I am!'; Try it Yourself » Declaring a JavaScript Variable Creating a variable in JavaScript is called "declaring" a variable. ...
If I enter 1.00 or 2.00 as my variable, the function will return false, even though the number I entered is in fact an integer.Javascript is_int() function example 2Some solutions propose doing a parseInt() on the value, and returning false if this is NaN:...
letmyModule={myProperty:"someValue",// 对象字面值包含了属性和方法(properties and methods).// 例如,我们可以定义一个模块配置进对象:myConfig:{useCaching:true,language:"en"},// 非常基本的方法myMethod:function(){console.log("Where in the world is Paul Irish today?");},// 输出基于当前配置co...
You can use theBoolean()function to find out if an expression (or a variable) is true: Example Boolean(10>9) Try it Yourself » Or even easier: Example (10>9) 10>9 Try it Yourself » Comparisons and Conditions The chapterJS Comparisonsgives a full overview of comparison operators. ...
if (firstName + lastName === "James Bond") 字符串的字符数量可以通过length属性获得: console.log( "Hello world!".length); // 12 所有的数字值都是在64位浮点数字。整数和浮点数之间没有明确的类型区别。如果一个数字常量不是数字,可以将其值设置为NaN(“not a number”),它可以用isNaN方法来判断。
if(number % 2==0){ //The number is even } else { //The number is odd } AlgorithmSTEP 1 ? Read the number to variable n. STEP 2 ? Divide n by 2 and save the remainder in a variable named r. STEP 3 ? If r==0, print "even" If r!=0, print "odd" Example...