This code counts the number of links in a page:
let temp = {}
for (const page of pages) {
let count = temp[page.outgoingLinks.length];
if (!count) {
count = 0;
}
count++;
temp[page.outgoingLinks.length]=count;
}
I would like to avoid the need for the if check that initializes the value.
In this example, the default value is an integer. But I would like to store even an Array there, something like defaultdict in python. How can I do it in JS?
There is nothing like Python's defaultdict in JavaScript, however you can have a default value when accessing the property by using the nullish-coalescing operator:
let count = temp[page.outgoingLinks.length] ?? 0;
To avoid the need for the if check that initializes the value
for (const page of pages) {
temp[page.outgoingLinks.length] = temp[page.outgoingLinks.length] ? temp[page.outgoingLinks.length]++ : 0;
}
here you can direclty use ternary operator to do so.
As you want multiple default values, you could create an object that contains the default values. This object can be defined in a helper function that takes an argument which specifies the type of default value you want and returns a function that can be called with the value.
If that value is undefined or null, this function returns the required type of default value.
function getInitializer(typeOfDefault) {
const defaults = {
arr: [0, 0, 0],
num: 0,
emptyString: ''
};
return (value) => value ?? defaults[typeOfDefault];
}
// default number
const initialize = getInitializer('num');
const a = initialize(0);
console.log(a);
// default array
const initialize2 = getInitializer('arr');
const b = initialize2(null);
console.log(b);