When working with TypeScript and JavaScript, we typically use either let or var to declare a variable. However, in Angular components, we do not use them even though Angular itself uses TypeScript. For instance,
export class ProductComponent implements OnInit {
productNumber = 5;
constructor() { }
ngOnInit() {
}
}
In the example above, we did not use let or var to define productNumber, yet it still functions as expected. Why is that?
const and let are used for declaring local variables in JavaScript. The code snippet you provided is actually defining a class field instead of a traditional local variable. Class fields have a different syntax compared to regular variables.
For instance, the code:
export class Example {
productNumber = 5;
}
Is essentially equivalent to this (which also doesn't utilize var or let):
export class Example {
constructor() {
this.productNumber = 5;
}
}
JavaScript assigns a specific memory space when declaring a variable with let or var. Each time you assign a value to the variable, you are essentially writing to that allocated memory space. These variables can be created as local variables inside a function or global variables within a file.
In this instance, productNumber is defined as a class member and specifies to the TypeScript compiler that there is a member variable with a default value of 5. The memory allocation occurs when an object of that class is instantiated in a file or function, like shown below:
let obj1 = new Sample(5);
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