How to use document.getElementById() method in TypeScript?

document.getelementbyid is not a function
document.getelementbyid(...) is null
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document.getelementbyid returning null

I am trying to reset HTML Form in order to clear all the values in the input fields using;

document.getElementById('myForm').reset(); 

But I can use that in typescript, it's giving me an error saying document.getElementById('myForm') may be null

How can I solve this issue?

Typescript will force you to check the value is not null if you use the strictNullChecks option (or strict which includes strictNullChecks). You can either perform the test or use a not null assertion (!). Also you will need to use a type assertion to assert the html element is an HTMLFormElement as by default it will be just an HtmlElement and reset is present only HTMLFormElement

Just an assertion Assertion:

(document.getElementById('myForm') as HTMLFormElement).reset();

Assertion with check (recommended):

let form = document.getElementById('myForm')
if(form) (form as HTMLFormElement).reset(); 

Not null assertion (if you want to access just HtmlElement member):

document.getElementById('myForm')!.click()

Document.getElementById(), Usage notes. The capitalization of "Id" in the name of this method must be correct for the code to function; getElementByID() is  The getElementById() method returns the element that has the ID attribute with the specified value. This method is one of the most common methods in the HTML DOM, and is used almost every time you want to manipulate, or get info from, an element on your document. Returns null if no elements with the specified ID exists.

There are different fixes for this. You can edit your tsconfig.json and add

"strictNullChecks": false

to it. This will disable the strict null checks.

If you are absolutely sure that the element exists, you could also use ! to tell typescript that your id will always be there

document.getElementById('myForm')!.reset(); 

Or if you want to make sure to never get an error because the element indeed doesn't exist, check for its existance

const el = document.getElementById('myForm');
if (el) el.reset();

Access an Element in Type Script, Then select HTML Application with TypeScript. STEP 2 innerText = "SUM"; button.onclick = function() {; var v = parseFloat(( < HTMLInputElement > document.getElementById("Text1")).value);; var v1 = parseFloat(( Next Recommended Article Dynamically Add Elements in Web Form Using TypeScript​. The task is select the elements with id by using the shorthand for document.getElementById with the help of JavaScript. we’re going to discuss few techniques. Approach 1: Define a function that returns the document.getElementById(‘idName’). This method takes IDName as the first and only argument. Call the method with ID as the argument.

Try a check on the element. Something like:

var myForm = document.getElementById('myForm');
if(myForm) myForm.reset();

Quick Reference To TypeScript, What is TypeScript; Data Type; Enum; Function; Function Overloading; Class & Object We know how to get div id using JavaScript. For catching div id, we have used document.getElementById. Price: number = 50.5;; Subject: string = "​TypeScript";; Value: any = 5;; constructor() {; console.log(this.Status);  Javascript uses various method to manage the validation and programming of a web page i.e. how to handle a web page is done by using Javascript. Javascript can change the HTML Content using the getElementById() method.

Handbook - DOM Manipulation, Using the DOM method "document.getElementById()" the text inside the paragraph tag is accessed and the value is displayed in the output. The first line of the TypeScript code uses a global variable document, inspecting the variable shows it is defined by the Document interface from the lib.dom.d.ts file. The code snippet contains calls to two methods, getElementById and createElement. Document.getElementById. The definition for this method is as follows:

How "getElementByID" works in JavaScript?, Handling DOM level events in Angular with typescript The scenario where we cannot make use of ViewElementRef class is some document.getElementById(​elementID) 2 functions focused() and focusedOut() were designed to highlight and remove the highlighting on the element that is focused. In order to access the form element, we can use the method getElementById() like this: var name_element = document.getElementById('txt_name'); The getElementById() call returns the input element object with ID ‘txt_name’ . Once we have the object, we can get the properties and call the methods of the object.

Handling DOM level events in Angular with typescript, Note: In HTML5, the "name" attribute is deprecated and has been replaced by the "id" attribute for many elements. Use the document.getElementById() method  (method) Document. getElementById (elementId: string): HTMLElement It looks like we have found our disconnect - at runtime there are two possible values (an HTMLElement object or null ), but at compile time TypeScript believes the return value will always be of one single type , HTMLElement .

Comments
  • Also, if myForm is not found, then it could indeed be a problem. TS doesn't know the layout of your page.
  • If you’re really sure the element exists, you could work around the default typing using !: document.getElementById('myForm')!.reset().
  • I'm using it with AngularJs, It's the controller where I can find myForm, But the problem is its giving me an error saying document.getElementById('myForm') may be null before compiling.
  • @RaphaelSchweikert document.getElementById('myForm')! this will work but later if i add .reset() it says [ts] Property 'reset' does not exist on type 'HTMLElement'. any.
  • Non null assertions are forbidden in ts > 3.4.5, just use assertion (the first one).
  • @Takatalvi Why are they forbidden? This is news to me, could you please provide some docs to that? Maybe you have a lint rule forbidding them but they are still a fuly supported part of the language
  • palantir.github.io/tslint/rules/no-non-null-assertion
  • @Takatalvi a tslint rule is just a lint rule. One can opt into it or not. There are plenty of code bases that do not opt into forbidding this operator, the TS compiler team being one of them. There is also a TS lint rule that forces you to specify all types which I personally find to be a horrible idea. Opting blindly into every rule is not a good idea.
  • Thanks for the clarification. I misunderstood the warning.
  • document.getElementById('myForm')! this will pass the null error but later if i add .reset() then it says [ts] Property 'reset' does not exist on type 'HTMLElement'. any