how to set multiple CSS style properties in typescript for an element?

Question

Please consider the below snippet. i need to set multiple CSS properties in typescript. for that i have tried the below code.

public static setStyleAttribute(element: HTMLElement, attrs: { [key: string]: Object }): void {
        if (attrs !== undefined) {
            Object.keys(attrs).forEach((key: string) => {
                element.style[key] = attrs[key];
            });
        }
    }

for the above code i need to pass the parameters as

let elem: HTMLElement = document.getElementById('myDiv');
setStyleAttribute(elem, {font-size:'12px', color : 'red' , margin-top: '5px'});

But the above code throws error(tslint) as Element implicitly has an 'any' type because index expression is not of type 'number'. (property) HTMLElement.style: CSSStyleDeclaration.

Please help me !!!

Henbit

error thrown in this line .......... element.style[key] – Henbit

Answer 1

Try using setAttribute. TypeScript does not have the style property on Element.

element.setAttribute("style", "color:red; border: 1px solid blue;");

Some related discussion in this GitHub issue: https://github.com/Microsoft/TypeScript/issues/3263

Breakfront

This code has the side effect, that it kills all old style definitions. – Vista

That's true! You'd need to use element.getAttribute('style') and merge the two together to maintain existing styles. – Breakfront

Answer 2

Just a little late to the party, but anyway...

The actual problem is not that style is not defined on Element. The word Element at the beginning of Element implicitly has an 'any' type because index expression is not of type 'number'. (property) HTMLElement.style: CSSStyleDeclaration is just the first word in a sentence and therefore uppercased. Means it does not relate in any way to the Element object - which is quite confusing.

However, the error message means that you are trying to access a property using the subscript operator [] with an incorrectly typed index. In your case your key is of type string but HTMLElement.style is a CSSStyleDeclaration object which has an index signature of [index: number]: string and consequently requires your key to be of type number.

The index signature comes from the typescript/lib/lib.dom.d.ts declaration file in your TypeScript installation. There you will find CSSStyleDeclaration.

So what you can do is simply cast to any like so:

(<any>element.style)[key] = attr[key];

It's not the best solution but it works and is straightforward. It also does not require you to stringify your styles like it would be necessary when you use element.setAttribute.

Starry

BTW: Does anyone know why the CSSStyleDeclaration in TypeScript's declarations file has that number-based index signature instead of a string-based? Makes no sense to me. – Starry

It reflects the browser. Try: myElement.style[0] to access the first style of myElement. – Vista

Here's the related issue on github github.com/microsoft/TypeScript/issues/17827 – Kerman

Answer 3

The API you were searching for is: https://developer.mozilla.org/en-US/docs/Web/API/CSSStyleDeclaration/setProperty

public static setStyleAttribute(element: HTMLElement, attrs: { [key: string]: string }): void {
    for(const [key, value] of Object.entries(attrs)) {
        element.style.setProperty(key, value);
    }
}

And hyphen is not allowed in object keys, so use ' here, too:

let elem: HTMLElement = document.getElementById('myDiv');
setStyleAttribute(elem, {'font-size':'12px', color: 'red', 'margin-top': '5px'});

Vista

This should be the accepted answer. TypeScript's CSSStyleDeclaration has number-based indexing (referenced in comments on other answers here) so string keys don't work. setProperty accepts string keys and has the same effect as style[key] = val without resorting to unsafe typing. Thanks @Vista – Ukrainian

This answer is useful, but element.style.setProperty(key, attrs[key]); will give an error since attrs[key] is an Object when the function expects a string. – Matrilocal

Wow. All the years and no one found the wrong type in the function signature! Thanks! I fixed the signature and changed to a for-of loop. – Vista

Answer 4

I hope this helps you or someone else...

You can achieve this using a HTLMDivElement and the CSSStyleDeclaration contained within it. eg.

var container: HTMLDivElement;

container.style.color = "red";
container.style.fontSize = "12px";
container.style.marginTop = "5px";

This also applies to other classes that inherit from HTMLElement and have a style property (for example HTMLBodyElement.

Gridley

may be for some one. not for my scenario..:) – Henbit

Answer 5

This problem was post in 06 Jun 2016，Typescript 2.1RC was release in 09 Nov 2016 that had new feature to solve the problem

After reading Typescript handbook and declaration for dom style, I had found the key of this problem that missing string index signature in Typescript declaration for dom style like following code:

interface CSSStyleDeclaration {
  accentColor: string;
  alignContent: string;
  // ....
  [index: number]: string;
}

It should be like this (so we can resolve the problem):

interface CSSStyleDeclaration {
  accentColor?: string;
  alignContent?: string;
  // ....
  [index: number]: string;
  [propName: string]: string;
}

I had used Utility Types to create a new Type for style and it worked:

type styleDeclaration = Partial<CSSStyleDeclaration> & { [propName: string]: string };

If you wanna learn more about this, you can take a look at this demo.

type styleDeclaration = Partial<CSSStyleDeclaration> & { [propName: string]: string };

const dom = document.createElement('div');

const styleObj: styleDeclaration = { width: '100px', height: '200px' };

Object.keys(styleObj).forEach((styleKey: string) => {
  (dom.style as styleDeclaration)[styleKey] = styleObj[styleKey];
});

Simulation

Answer 6

you can use this for a single element, and iterate over it to make it dynamic

let el: HTMLElement = document.getElementById('elementID');

el.style.height = "500px";

Salol

I've used this with TypeScript / Angular. Normally, document.getElementById() can return as an Element type, make sure you use let el: HTMLElement = <HTMLElement>document.getElementById('elementID'); to change it. Thanks! – Garrow

Answer 7

An unsafe / untyped way:

const e = document.createElement("div")
Object.assign(e.style, {borderSize: "1rem", verticalAlign: "middle"})

You'll need to convert standard CSS style naming to the TypeScript alternatives for this to work. i.e. font-size vs. fontSize. Be warned: You will get no errors on a bad style name. {attrFOO: "bar"} is valid.

Adena