JavaScript in Practice: Getting Started/

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Restricted Deep Copy Implementations

Restricted Deep Copy Implementations

Learn about two methods to implement deep copy and their limitations.

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JSON methods

There is a very easy implementation for making deep copies of JavaScript objects. Convert the JavaScript object into a JSON string, then convert it back into a JavaScript object.

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a = []; 
a.b = 'language hack';
//comment the above a.b = 'language hack' and uncomment below line
//a = new Date(2011,0,1);
var deepCopy = function( o ) {
    return JSON.parse(JSON.stringify( o ));
}
var cloned_a = deepCopy( a );
console.log( 'cloned_a.b = ', cloned_a.b );
//comment the line 9 and uncomment the below line to see the output of line 4
//console.log( 'cloned_a = ', cloned_a );

Restrictions:

  • Object o has to be finite; otherwise, JSON.stringify throws an error.

  • The JSON.stringify ...