Add value if not exists Loop through the array to check whether a particular username value already exists and if it does do nothing, but if it doesn’t add a new object to the array. const arr = [{ id: 1, username: 'fred' }, { id: 2, username: 'bill' }, { id: 3,...
Discover how to efficiently check if a value exists in an array using JavaScript. Learn essential techniques for seamless array manipulation.
varfruits=["Apple","Banana","Mango","Orange","Papaya"];// Check if a value exists in the fruits arrayif(fruits.indexOf("Mango")!==-1){alert("Value exists!")}else{alert("Value does not exists!")} ES6 has introduced theincludes()method to perform this task very easily. But, ...
; var valueToCheck = "sample"; if (textField.indexOf(valueToCheck) !== -1) { console.log("The value exists in the text field."); } else { console.log("The value does not exist in the text field."); } 在上述代码中,我们定义了一个文本字段textField和要检查的值valueT...
You can use the Object.prototype.hasOwnProperty() method to check if a key exists in a JSON object in the following way: const jsonObj = { key1: 'value1', }; console.log(jsonObj.hasOwnProperty('key1')); // true console.log(jsonObj.hasOwnProperty('key2')); // false ...
constcheckKey =(obj, keyName) =>{letkeyExist =Object.keys(obj).some(key=>key === keyName);console.log(keyExist); }; checkKey(user,'name');// Return true Usingsome()for an Array letnumber = [12,33,14,45];// Check if key existsnumber.some(value=>value ===1);// Returns ...
3 check if value exists in json array 0 JSON - If Object's Value Equals 2 How to compare two JSON values based on the key name in javascript? 15 How to check if values in one JavaScript object are present in another one? 0 Comparing array values in javascript 0 Javascript check ...
save(function(err) { if (err) done(err); else done(); }); }); }); }); Alternatively, just use the done() callback directly (which will handle an error argument, if it exists): describe('User', function() { describe('#save()', function() { it('should save without error'...
if(!String.prototype.startsWith){ String.prototype.startsWith = function (str) { return !this.indexOf(str); } } "Hello World!".startsWith("He"); // true var data = "Hello world"; var input = 'He'; data.startsWith(input); // true Checking whether the function already exists in...
它是用三点(...)表示,Array是可以扩展的,如果是Object,会按照key-value进行扩展。 代码语言:javascript 代码运行次数:0 复制 Cloud Studio代码运行 conststuendts=['Angel','Ryan'];constpeople=['Sara',...stuendts,'Kelly','Eason'];conslog.log(people);// ["Sara", "Angel", "Ryan", "Kelly", ...