Javascript immutable array manipulation

array_manipulation.js

//Adding to an array without mutating the original

return list.concat(item);

//---------------------------------------------------------
//Deleting an item in an array without mutating the original

return list
	.slice(0, index)
	.concat(list.slice(index + 1));

//or in ES6
return [
	...list.slice(0, index),
	...list.slice(index + 1) 
	];

//---------------------------------------------------------
//Updating an item in an array without mutating the original

return list
	.slice(0, index)
	.concat([list[index] + 1] //in this case increment by one but replace with more complex structure
	.concat(list.slice(index + 1));
          
//or in ES6
return [
	...list.slice(0, index),
	list[index] + 1,  //in this case increment by one but replace with more complex structure
	...list.slice(index + 1)
	];