Advanced-JavaScript-With-Projects/shallowDeepRestOperator.html at main · marleyDip/Advanced-JavaScript-With-Projects · GitHub

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<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Array Method</title>
  </head>
  <body></body>
  <script>
    let l = [10, 20, 30, 40, 50];

    let m = l;
    m.push(99);

    console.log(l); // if m changes anything, l will be changed
    console.log(m); // deep copy....l behavior also be copy in m

    let l1 = [10, 20, 30, 40, 50];

    let m1 = [...l]; // ...rest operator = Collects elements
    m.push(99);

    console.log(l1); // here not changed anything, bcz m = ... just only copy the values

    console.log(m1); // shallow copy... only copy the values of l, not behavior

    // l.push(99);
    // console.log(l);

    /* A shallow copy creates a new object/array that copies the top-level structure of the original,

    but references the same underlying objects for nested properties/elements. */

    const l3 = [10, 20, 30, [40, 50]];

    const m3 = [...l3];

    // Top-level property changed - doesn't affect original
    m3[0] = 100;

    // Nested property changed - affects original! reference value
    m3[3][0] = 200;

    console.log(l3); // 10 unchanged but 40 changed to 200
    console.log(m3);

    console.log(l3.join(", ")); //10, 20, 30, 200,50
    console.log(m3.join(", ")); // 100, 20, 30, 200,50
  </script>
</html>