Javascript - Functions, missing argument

user_14200358 0
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Baby coder here, just getting into functions. I've created a function to calculate the area of a rectangle, and it works as long as two arguments are provided. I want my code to assume the shape is a square (so length and width are equal), if only one argument is provided. I've been trying to come up with a conditional, but don't know how to say "if there is only one argument, then length === width". Any pointers appreciated!

function area(length, width) {
    let rectangleArea = Number(length) * Number(width);
    return rectangleArea;
}
console.log(area(10, 5));

conditional-statements arguments function javascript
2 Answers

One option is to use a default function parameters for the width parameter and set it to length if it is not passed

function area(length, width = length) {
  let rectangleArea = length * width;
  return rectangleArea;
}

console.log(area(10, 5));
console.log(area(10));

Default function parameters is a recent feature. If it is confusing, you could check if width parameter is undefined and set it to length

function area(length, width) {
  if (typeof width === "undefined")
    width = length;

  let rectangleArea = length * width;
  return rectangleArea;
}

console.log(area(10, 5));
console.log(area(10))

Also, the Number() wrapper is not required here. You are already passing numbers. Even if you pass strings as parameters like area("10", "5"), they are coerced to numbers and multiplied.

user_30822960

You may use default parameter width = length. If the value of width is not passed to the function, the value of length will be assigned to the width.

function area(length, width = length) {
    let rectangleArea = Number(length) * Number(width);
    return rectangleArea;
}

console.log(area(10, 5));
console.log(area(10));
console.log(area(5));

user_110579880
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