The findIndex() method executes the callback function once for every index in the array until it finds the one where callback returns a truthy value (that is, a value that coerces to true). If such an element is found, findIndex() immediately returns the element's index. An array can hold many values under a single name, and you can access the values by referring to an index number. Creating an Array Using an array literal is the easiest way to create a JavaScript Array. At the implementation level, JavaScript's arrays actually store their elements as standard object properties, using the array index as the property name. The length property is special. It always returns the index of the last element plus one. (In the example below, 'Dusty' is indexed at 30, so cats.length returns 30 + 1). The JavaScript indexof method returns the index position of the first occurrence of a specified string. If the specified string not located, the indexof function will return -1. The syntax of the JavaScript indexof function is Every function in JavaScript returns undefined unless otherwise specified. To test this, we’ll just create an empty function, then invoke it: function test(){}; test(); // undefined. As expected, when we invoke our function undefined is returned in the console. Now we’ll actually specify a return value. JavaScript IndexOf method return the index position of the first occurrence of a specified string. If the string is not found, JavaScript indexof return -1. JavaScript IndexOf method return the index position of the first occurrence of a specified string. If the string is not found, JavaScript indexof return -1. JavaScript String - indexOf() Method - This method returns the index within the calling String object of the first occurrence of the specified value, starting the search at fromIndex or -1 if the val
15 Apr 2019 The JavaScript includes method finds the target in an Array or the target string the method returns the first character index (string) or 12 Aug 2017 A Better Way to Perform Multiple Comparisons in JavaScript indexOf() returns the value's position, so we only have to make sure the result is index.html --> < script src="polyfills/indexOf.js">