Array Cheat Sheet

posted in ..

Note, all methods that are marked with an exclamation mark (!) will mutate their object. All italicized parameters are optional.

Static Methods

isArray(obj)
var a = [[],[1],2,"3"];
a.map(Array.isArray);
  //-> [true,true,false,false]

Instance Properties

constructor

length

Instance Methods

concat(args,)
[1,2].concat(3,4);
  //-> [1,2,3,4]
[1,2].concat([3,4],[5,6]);
  //-> [1,2,3,4,5,6]
every(callback, thisObj)
function decr(n,i,ary) {
  return n - 1;
}
[1,2,3].every(decr);
  //-> false
[2,3].every(decr);
  //-> true
filter(callback, thisObj)
function decr(n,i,ary) {
  return n - 1;
}
[1,2,3].filter(decr);
  //-> [2,3]
forEach(callback, thisObj)
[1,2,3].forEach(alert);
  // 3 alerts
indexOf(searchArg, fromIndex)
[1,2,3].indexOf(3);
  //-> 2
join(separator)
[1,2,3].join();
  //-> "1,2,3"
[1,2,3].join("+");
  //-> "1+2+3"
lastIndexOf(searchArg, thisObj)
[1,2,3].indexOf(3);
  //-> 2
map(callback, thisObj)
function decr(n,i,ary) {
  return n - 1;
}
[1,2,3].map(decr);
  //-> [0,1,2]
pop()!
var a = [1,2,3];
a.pop();
  //-> 3
a;
  //-> [1,2]
push(args,)!
var a = [1,2];
a.push(3, 4);
  //-> 4
a;
  //-> [1,2,3,4]
reduce(callBack, initialValue)
function sub(p,n,i,ary) {
  return p - n;
}
[1,2,3].reduce(sub);
  //-> -4
reduceRight()
function sub(p,n,i,ary) {
  return p - n;
}
[1,2,3].reduceRight(sub);
  //-> 0
reverse()!
var a = [1,2,3];
a.reverse(); a;
  //-> [3,2,1]
shift()!
var a = [1,2,3];
a.shift();
  //-> 1
a;
  //-> [2,3]
slice(begin, end)
[1,2,3].slice(1,2);
  //-> [2]
some(callback, thisObj)
[1,2,3].some(function(n,i,ary) {
  return n - 1;
});
  //-> true
sort(compareFunction)!
var a = [2,3,1];
a.sort(); a;
  //-> [1,2,3]
function longer(a,b) {
  return a.length > b.length? 1:
    a.length < b.length? -1: 0;
}
a = ["aardvark","beaver","cat"]
a.sort(longer);
  //-> ["cat","beaver","aardvark"]
splice(index, howMany, args,)!
var a = [1,2,3];
a.splice(1,2,4,5);
  //-> [2,3]
a;
  //-> [1,4,5]
unshift(args,)!
var a = [1,2];
a.unshift(3,4);
  //-> 4
a;
  //-> [1,2,3,4]
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