_indexOf.js•1.42 kB
var equals = require('../equals');
module.exports = function _indexOf(list, a, idx) {
var inf, item;
// Array.prototype.indexOf doesn't exist below IE9
if (typeof list.indexOf === 'function') {
switch (typeof a) {
case 'number':
if (a === 0) {
// manually crawl the list to distinguish between +0 and -0
inf = 1 / a;
while (idx < list.length) {
item = list[idx];
if (item === 0 && 1 / item === inf) {
return idx;
}
idx += 1;
}
return -1;
} else if (a !== a) {
// NaN
while (idx < list.length) {
item = list[idx];
if (typeof item === 'number' && item !== item) {
return idx;
}
idx += 1;
}
return -1;
}
// non-zero numbers can utilise Set
return list.indexOf(a, idx);
// all these types can utilise Set
case 'string':
case 'boolean':
case 'function':
case 'undefined':
return list.indexOf(a, idx);
case 'object':
if (a === null) {
// null can utilise Set
return list.indexOf(a, idx);
}
}
}
// anything else not covered above, defer to R.equals
while (idx < list.length) {
if (equals(list[idx], a)) {
return idx;
}
idx += 1;
}
return -1;
};