peek operation in stack using javascript

Question

How can I get the first element from my stack here is my code

var stack = []; stack.push(id1); stack.push(id2); 

I know there is something like peek in java. Is there any similar method in JS using which i can get the topmost element?

Answer 1

To check the topmost element unfortunately you must explicitly index it

var top = stack[stack.length-1]; 

the syntax stack[-1] (that would work in Python) doesn't work: negative indexes are valid only as parameters to slice call.

// The same as stack[stack.length-1], just slower and NOT idiomatic var top = stack.slice(-1)[0]; 

To extract an element there is however pop:

// Add two top-most elements of the stack var a = stack.pop(); var b = stack.pop(); stack.push(a + b); 

Answer 2

var stack = [];  stack.push("id1");  stack.push("id2");  console.log(stack[stack.length-1]); // the top element  console.log(stack.length); //size