How does the slice() function work with the push() function in Javascript?

Question

Here the output for a and b is same but in case of slice() we didn't pass any parameter so the output for a, b, and c must be same. So why is the output of c different from a and b here?

<!DOCTYPE html>
        <html>
        <head>
        </head>
        <body>
        <p id="1"></p>
        <p id="2"></p>
        <p id="3"></p>
        <p id="4"></p>
        <script>
        var a=["a","b","c"];
        var b=a;
        var c=a.slice();
        a.push("date");
        document.getElementById("1").innerHTML=a;
        document.getElementById("2").innerHTML=b;
        document.getElementById("3").innerHTML=c;
        document.getElementById("4").innerHTML=a;

        </script>
        </body>
        </html>

Output:

a,b,c,date
a,b,c,date
a,b,c
a,b,c,date

You re slicing an original array before push new value into the array which is 'date' — digit
– digit, Commented Jan 3, 2017 at 5:33

Daniel Bank · Accepted Answer · 2017-01-03 05:36:19Z

3

From MDN:

The slice() method returns a shallow copy of a portion of an array into a new array object selected from begin to end (end not included). The original array will not be modified.

So c is a copy of a whereas b is a reference to it. Thus when you modify a, b changes but c does not.

answered Jan 3, 2017 at 5:36

Daniel Bank

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Amit Jamwal · Accepted Answer · 2017-01-03 05:37:11Z

0

you are slice your array before pushing a new element. Also slice returns a new array so the reference of "a" array is not impacting your "c" array.

hope this helps...

answered Jan 3, 2017 at 5:37

Amit Jamwal

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prasanth · Accepted Answer · 2017-01-03 05:37:20Z

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a.slice() inside the slice function not declare any value .so not perform any action.And a.slice() != a .Because you are declare the c=a.slice() before push into the array. Slice() not change array values.Its will duplicate array value pass to the c array. If you need ah date just push with array of c

var a=["a","b","c"];
        var b=a;
        var c=a.slice();
        a.push("date");
        c.push('date')
        document.getElementById("1").innerHTML=a;
        document.getElementById("2").innerHTML=b;
        document.getElementById("3").innerHTML=c;
        document.getElementById("4").innerHTML=a;

<p id="1"></p>
        <p id="2"></p>
        <p id="3"></p>
        <p id="4"></p>

answered Jan 3, 2017 at 5:37

prasanth

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