.indexOf function on an array not working in IE7/8 using JavaScript

Question

Can anyone tell me if IE 7 and IE 8 support the JavaScript .indexOf() method as I am receiving the error:

SCRIPT438: Object doesn't support property or method 'indexOf' 

from the IE9 debug console (used under both IE7 and IE8 Browser mode).

For the below comment, the code using .indexOf() is as follows:

if(shirt_colour == 'black') {
 p_arr=['orange','red','green','yellow','bblue','rblue','pink','white','silver','gold'];
 if( p_arr.indexOf(print_colour) != -1 ) rtn = true;
}

• Guidhouse: I've used indexOf() since IE3/Netscape 4.7, never with that problem. Are you sure you're using it on a string object? show us the code that returns the error.
• Gga: @Guidhouse Any thoughts then based on the above? I would have certainly thought quite a rudimentary function like that would be in IE7.
• Guidhouse: The answer to this question does express any thought I have on the subject very well. So i just give that a vote up instead :-)

Answer 1

On IE<9 indexOf() it is not "well" implemented. Try to add this function on your code :

if (!Array.prototype.indexOf)
{
 Array.prototype.indexOf = function(elt /*, from*/)
 {
 var len = this.length;
 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;
 };
}

It will "replace" the original function, if not found in the ECMA-262 standard.

Answer 2

Following code can be helpful.

function findIndexOf(findfrom, findthis) {
 for (i = 0; i < findfrom.length; i++) {
 if (findfrom[i] == findthis) {
 return i;
 }
 }
 return -1;
}

Answer 3

If you need indexOf in IE<=8, you should consider using the following polyfill, which is recommended at the MDN :

// Production steps of ECMA-262, Edition 5, 15.4.4.14
// Reference: http://es5.github.io/#x15.4.4.14
if (!Array.prototype.indexOf) {
 Array.prototype.indexOf = function(searchElement, fromIndex) {
 var k;
 // 1. Let o be the result of calling ToObject passing
 // the this value as the argument.
 if (this == null) {
 throw new TypeError('"this" is null or not defined');
 }
 var o = Object(this);
 // 2. Let lenValue be the result of calling the Get
 // internal method of o with the argument "length".
 // 3. Let len be ToUint32(lenValue).
 var len = o.length >>> 0;
 // 4. If len is 0, return -1.
 if (len === 0) {
 return -1;
 }
 // 5. If argument fromIndex was passed let n be
 // ToInteger(fromIndex); else let n be 0.
 var n = +fromIndex || 0;
 if (Math.abs(n) === Infinity) {
 n = 0;
 }
 // 6. If n >= len, return -1.
 if (n >= len) {
 return -1;
 }
 // 7. If n >= 0, then Let k be n.
 // 8. Else, n<0, Let k be len - abs(n).
 // If k is less than 0, then let k be 0.
 k = Math.max(n >= 0 ? n : len - Math.abs(n), 0);
 // 9. Repeat, while k < len
 while (k < len) {
 // a. Let Pk be ToString(k).
 // This is implicit for LHS operands of the in operator
 // b. Let kPresent be the result of calling the
 // HasProperty internal method of o with argument Pk.
 // This step can be combined with c
 // c. If kPresent is true, then
 // i. Let elementK be the result of calling the Get
 // internal method of o with the argument ToString(k).
 // ii. Let same be the result of applying the
 // Strict Equality Comparison Algorithm to
 // searchElement and elementK.
 // iii. If same is true, return k.
 if (k in o && o[k] === searchElement) {
 return k;
 }
 k++;
 }
 return -1;
 };
}