Avoid using var to declare variables, whenever possible.
Use const to declare variables, unless the variable needs to be reassigned. If the latter is true, use let.
Clean code: declare the variables at the top of each scope.
Clean code: declare functions before using them.
Don't use arrow functions as methods, because the this keyword will point to the parent function/object, and not to the object calling the method. Always use function declarations.
We should use functions instead of writing code directly on the global scope, and pass variables to functions as arguments instead of using global variables.
It's a bad practice to mutate function parameters, so when a parameter needs to be modified inside a function, it's better to create a copy of that parameter and modify that copy.
It's a bad practice to chain methods that mutate the original array, such as the splice() method.
If there is a variable that we must define but is not going to be used, we should name it _ :
const myArr_4 = Array.from({ length: 7 }, (_, i) => i + 1);
console.log(myArr_4);
// -> [1, 2, 3, 4, 5, 6, 7]