Check if string starts with a lowercase.Check if string starts with an uppercase.Check if string starts with specific character.Check if string ends with specific substring.Check if string starts with specific substring.Check if string contains specified substring. Check if strings are equal ignoring case.The polyfill works well with browsers that are compatible with ES3 specifications and works across frames. However, if the browsers you're targeting lack the support, you can use a polyfill for it which is given below. The Array.isArray method has very good browser support as it is part of the ES5 specification. True, but length property can return that the variable is empty even for non-array variables so we need to ensure that we are dealing with an array first before using the length property. One obvious question we might have is why not just use the length property at the beginning itself? Won't it make the code simpler? If the length of the array is 0, then the array is empty otherwise it is not empty. Once we have made sure we are dealing only with an array, we can easily check if the array is empty or not using the length property. This may lead to unexpected results when using instanceof, for example, for scripts passing objects from one context to another via functions.Ĭonsidering such cases, it is best to simply use Array.isArray, especially when creating a framework, library, or a plugin, where the environment in which it will be used is not known in advance. different global objects, different constructors, etc.). This means that they have different built-in objects (i.e. The reason for this is that in javascript each window or frame has its own execution environment, thus having a different scope from each other. While instanceof can be used for most cases in place Array.isArray, the Array.isArray is preferred over instanceof as it works through multiple contexts (such as frames or windows) correctly whereas instanceof does not. To illustrate this, consider for example: const array = Ĭonsole.log(typeof array) // output: 'object'Ĭonsole.log(array instanceof Array) // output: trueĬan we use instanceof instead of Array.isArray? The answer is NO, because an array in JavaScript is an instance of the Array object and typeof would return the type object for it. The Array.isArray() returns False for the following cases Array.isArray() Ĭan we use typeof instead of the Array.isArray? Note: Array.prototype itself is an array so the function Array.isArray() returns TRUE. The Array.isArray() method returns true for the following cases Array.isArray() Īrray.isArray(new Array('apple', 'mango', 'grapes')) The Array.isArray() method is a sure shot method to check if a variable is an array or not and it automatically eliminates the cases of null and undefined without writing an additional script to check for it. Here, since the array is empty, the function returns True.In the second case, arrTwo, it is again an array and so passes into the second condition.
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