Javascript If statement, looking through an array

Question

Mind has gone blank this afternoon and can't for the life of me figure out the right way to do this:

if(i!="3" && i!="4" && i!="5" && i!="6" && i!="7" && i!="8" && i!="9" && i!="2" && i!="19" && i!="18" && i!="60" && i!="61" && i!="50" && i!="49" && i!="79" && i!="78" && i!="81" && i!="82" && i!="80" && i!="70" && i!="90" && i!="91" && i!="92" && i!="93" && i!="94"){
//do stuff
}

All those numbers need to be in an array, then I can check to see if "i" is not equal to any 1 of them.

• fearofawhackplanet: see stackoverflow.com/questions/237104/javascript-array-containsobj
• Evan Carroll: possible duplicate of Best way to find an item in a JavaScript Array ?
• Evan Carroll: @fearofawhackplanet, you're right too. I've marked that function as a dupe as well.

Answer 1

var a = [3,4,5,6,7,8,9];
if ( a.indexOf( 2 ) == -1 ) { 
 // do stuff
}

indexOf returns -1 if the number is not found. It returns something other than -1 if it is found. Change your logic if you want.

Wrap the numbers in quotes if you need strings ( a = ['1','2'] ). I don't know what you're dealing with so I made them numbers.

IE and other obscure/older browsers will need the indexOf method:

if (!Array.prototype.indexOf) 
{ 
 Array.prototype.indexOf = function(elt /*, from*/) 
 { 
 var len = this.length >>> 0; 
 var from = Number(arguments[1]) || 0; 
 from = (from < 0) 
 ? Math.ceil(from) 
 : Math.floor(from); 
 if (from < 0) 
 from += len; 
 for (; from < len; from++) 
 { 
 if (from in this && 
 this[from] === elt) 
 return from; 
 } 
 return -1; 
 }; 
} 

• fearofawhackplanet: seeing this just makes me love jQuery even more.

Answer 2

My mind made this solution:

function not(dat, arr) { //"not" function
for(var i=0;i<arr.length;i++) {
 if(arr[i] == dat){return false;}
}
return true;
}
var check = [2,3,4,5,6,7,8,9,18,19,49,50,60,61,70,78,79,80,81,82,90,91,92,93,94]; //numbers
if(not(i, check)) {
//do stuff
}

• meder omuraliev: One benefit of using indexOf is that it's already built into most modern browsers.

Answer 3

This solution is cross-browser:

var valid = true;
var cantbe = [3, 4, 5]; // Fill in all your values
for (var j in cantbe)
 if (typeof cantbe[j] === "number" && i == cantbe[j]){
 valid = false;
 break;
 }

valid will be true if i isn't a 'bad' value, false otherwise.

• Andy E: It's very bad practice to use for...in on arrays.
• Chris Laplante: I wouldn't call it bad practice, as long as you know what you're doing. I've added a check: typeof cantbe[j] === "number".
• Christian C. Salvadó: @SimpleCoder, because for-in is meant to enumerate object properties, to iterate over array objects, a sequential loop is always the best, more details here.