When to use return in JavaScript function ?

 Excellent — this is a JavaScript arrow function + map() example! 👇

Let’s go through it step by step:

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🧠 Code:

let a = ["Ram", "shyam"]

let r = a.map(x => x.toUpperCase())
console.log(r)

let t = a.map(x => {
    return x.toUpperCase()
})
console.log(t)

let y = a.map(x => (
    x.toUpperCase()
))
console.log(y)

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🔍 1️⃣ map() method:

• The .map() method creates a new array by applying a function to each element of the original array.

• It does not modify the original array.

Example:

["Ram", "shyam"].map(x => x.toUpperCase())

➡️ It will take each element:

• "Ram" → "RAM"

• "shyam" → "SHYAM"
  and return a new array ["RAM", "SHYAM"].

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🧩 2️⃣ let r = a.map(x => x.toUpperCase())

✅ Short arrow function
If there’s only one expression, you can omit {} and return.
It automatically returns the result.

So:

x => x.toUpperCase()

means “take x and return x.toUpperCase()”.

🟢 Output: ["RAM", "SHYAM"]

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🧩 3️⃣ let t = a.map(x => { return x.toUpperCase() })

✅ Long form with braces {}
When you use {}, you must explicitly write return.
Otherwise, it won’t return anything.

🟢 Output is same: ["RAM", "SHYAM"]

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🧩 4️⃣ let y = a.map(x => ( x.toUpperCase() ))

✅ Parentheses form ( )
When you wrap the expression inside parentheses, it’s like saying:

"Return this expression's value"

So this is also equivalent to the first one.

🟢 Output: ["RAM", "SHYAM"]

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📦 Final Output:

[ 'RAM', 'SHYAM' ]
[ 'RAM', 'SHYAM' ]
[ 'RAM', 'SHYAM' ]

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⚙️ Summary Table:

Code Form	Requires return?	Output
x => x.toUpperCase()	❌ No	["RAM", "SHYAM"]
x => { return x.toUpperCase() }	✅ Yes	["RAM", "SHYAM"]
x => ( x.toUpperCase() )	❌ No	["RAM", "SHYAM"]