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Alvin Lucillo

Const assertion

/ 1 min read

ts

💻 Tech

To declare an object with immutable properties, you can use const assertion. This can be used as constants values across your app.

export const icons = { icon1: 'icon1', icon2: 'icon2', icon3: 'icon3' } as const;

With this, you can safely use icons.icon1 without the risk of its value being changed in some parts of the code. Without as const, the value of properties like icon1 can be changed.

For example, the code below will result to an error.

const icons = { icon1: 'icon1', icon2: 'icon2', icon3: 'icon3' } as const;

icons.icon1 = ""; // Cannot assign to 'icon1' because it is a read-only property.

Another example, the code below will not result to an error because the properties of icons are mutable.

const icons = { icon1: 'icon1', icon2: 'icon2', icon3: 'icon3' };

icons.icon1 = "";