I have a js 2d array
var a = [["a","b","c","d","e","f"]]
I need to discard the last and insert at the first position
var result = [["new","a","b","c","d","e"]] //<------ "f" has to be discarded
I have tried with
a.unshift("new")
How do I do it?
Use unshift to add new values to the beginning of the array and pop to remove values from the end.
let a = ["a", "b", "c", "d", "e", "f"];
a.unshift('new');
a.pop();
console.log(a);Also, in your example - a is an array within array, so perform this on the inner array.
To be even more generic, you can extract this to function and perform this on every inner array with map:
let a = [
["a", "b", "c", "d", "e", "f"]
];
let result = a.map(innerArr => {
innerArr.unshift('new');
innerArr.pop();
return innerArr;
});
console.log(result);
unshift() and pop() solves your problem.
You can first splice it and then use unshift
var a = [
["a", "b", "c", "d", "e", "f"]
]
a[0].splice(-1, 1);
a[0].unshift('new');
console.log(a)
var a = [["a","b","c","d","e","f"]]
a[0].unshift('new');
a[0].pop();
console.log(a);