Aprenda Using Function Arguments Effectively

Arguments are function variables that you can use only inside the function:


              12345678
            
function funcName(a, b) {
  console.log("Arg A =", a);
  console.log("Arg B =", b);
};

funcName(15, 24);

console.log(a);  // This will raise an Error

Also, if you name the arguments the same as the variables outside the function, the function will use the arguments instead of the variables:


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let a = 15;

function num(a) {
  console.log("(func) a =", a);
};

num(20);

console.log("(global) a =", a);

Note

When the function finishes execution, its space disappears, and all arguments lose their values.

Arguments are received sequentially:


              12345
            
function numSet(a, b, c) {
  console.log([a ** 2, b + 2, c - 10]);
};

numSet(15, 12, 99);

Unfilled arguments will receive the value undefined and will not be displayed in any way. Redundant arguments will not be used:


              123456
            
function numSet(a, b, c) {
  console.log([a, b, c]);
}

numSet(12, 13);
numSet(15, 12, 13, 15);

The function receives values as arguments. Variables outside the function remain unchanged. An argument is an independent value inside a function:


              12345678910
            
let a = 15;

function add(numb) {
  numb += 5;
  console.log("(func) numb =", numb);
};

add(a);

console.log("(global) a =", a);

Note

This does not work the same way for arrays because an array contains a reference to some data. This reference is passed to the function, so changes inside the function affect the data outside. This will be studied in the "OOP in JavaScript" course.

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