How to remove a specific element in array in JavaScript

var newArray = [];
var a=["a","b","c"];
for(var i=0;i<a.length;i++)
    if(a[i]!=="a") 
        newArray.push(a[i]);

As of newer versions of JavaScript:

var a = ["a","b","c"];
var newArray = a.filter(e => e !== "a");

remove = function(ary, elem) {
    var i = ary.indexOf(elem);
    if (i >= 0) ary.splice(i, 1);
    return ary;
}

provided your target browser suppports array.indexOf, otherwise use the fallback code on that page.

If you need to remove all equal elements, use filter as Rocket suggested:

removeAll = function(ary, elem) {
    return ary.filter(function(e) { return e != elem });
}