What's the best way to remove properties and functions from an object in Javascript?

Theres is tow Option:

1- Delete is the true way to remove object's properties without any leftovers, but it works slow

2- setting object[key] = undefined.

Example:

Delete: 

Var obj ={ feild:1 }; 

delete obj.feild;

Undefined: 

Var obj ={ feild:1 }; 

obj.feild=undefined;

this may help you 

using "delete" keyword

Example:

delete myObject.aProperty;

You can Use Delete Statement to remove this.

eg. Delete obj.property

Simply use the Delete key word

Example: 

var test ={'red':'#FF','blue':'#FF'};

delete test.blue;