Could converting a 47-byte JSON string into 340 MB be possible through JSON stringification?

Question

Could converting a 47-byte JSON string into 340 MB be possible through JSON stringification?

var keys = [7925181,"68113227"];
var vals = {"7925181":["68113227"],"68113227":["7925181"]};

var temp = [];
for (var i = 0; i < keys.length; i++) {
    temp[keys[i]] = vals[keys[i]];
}
//alert(JSON.stringify(vals).length);
alert(JSON.stringify(temp).length);

After running this script in my Chrome browser, I was surprised to see an output of 340666156 after some time.

This raises the question... how did that happen?

The commented out alert function gives an output of 47. Shouldn't the second alert show a similar result? Isn't temp supposed to be a duplicate of val?

You can find a jsfiddle with the code here:

http://jsfiddle.net/vMMd2/

Additionally, if you want to test browser crashes (Chrome crashed for me), you can add the following snippet at the end:

temp.forEach(function(entry) {
    alert(temp);
});

Any thoughts or insights on this issue?

javascript json

Answer 1

Answer №1

const items = [10581223,"32197654"];
const data = {"10581223":["32197654"],"32197654":["10581223"]};

const temporaryData = {};
for (let index = 0; index < items.length; index++) {
    temporaryData[items[index]] = data[items[index]];
}
//alert(JSON.stringify(data).length);
alert(JSON.stringify(temporaryData).length);

http://jsfiddle.net/zerkms/vMMd2/2/

By creating a sparse array, V8 may initialize all the gaps with certain values like undefined (as discovered by nnnnnn). This process takes some time.

Answer 2

const items = [10581223,"32197654"];
const data = {"10581223":["32197654"],"32197654":["10581223"]};

const temporaryData = {};
for (let index = 0; index < items.length; index++) {
    temporaryData[items[index]] = data[items[index]];
}
//alert(JSON.stringify(data).length);
alert(JSON.stringify(temporaryData).length);

http://jsfiddle.net/zerkms/vMMd2/2/

By creating a sparse array, V8 may initialize all the gaps with certain values like undefined (as discovered by nnnnnn). This process takes some time.

Answer 3

Answer №2

According to @zerkms, this situation is occurring for a reason. However, I also wanted to highlight why it's happening.

> var temp = [];
> temp[10] = 'test';
> temp 
[ , , , , , , , , , , 'test' ]

It's evident that 9 undefined values are being created. When I executed the above code with nodejs, the null values were not visible.

If I were to use JSON.stringify(), the result would be:

> JSON.stringify(temp)
'[null,null,null,null,null,null,null,null,null,null,"test"]'

Answer 4

According to @zerkms, this situation is occurring for a reason. However, I also wanted to highlight why it's happening.

> var temp = [];
> temp[10] = 'test';
> temp 
[ , , , , , , , , , , 'test' ]

It's evident that 9 undefined values are being created. When I executed the above code with nodejs, the null values were not visible.

If I were to use JSON.stringify(), the result would be:

> JSON.stringify(temp)
'[null,null,null,null,null,null,null,null,null,null,"test"]'

Could converting a 47-byte JSON string into 340 MB be possible through JSON stringification?

Answer №1

Answer №2

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