As I delve into the angular documentation, I notice that all classes have properties defined in a specific way:
class A {
a = 2;
};
However, in the TypeScript official documents, the class properties are declared differently:
class A {
a:2
}
I'm curious to know why there is this difference and which one is considered correct?
When you use the = sign, it creates a class member with the value of 2. On the other hand, the : seems to create a property with the type 2, but its actual value is undefined.
This distinction is clearly observable in the transpiled code.
For example:
class A {
x: 2;
y = 2;
method() {
console.log(this.x)
}
}
console.log(new A().x)
After transpilation:
var A = (function () {
function A() {
this.y = 2;
}
A.prototype.method = function () {
console.log(this.x);
};
return A;
}());
console.log(new A().x);
You can test and verify this behavior in the TypeScript playground by clicking here.
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