Remove findIndex polyfill

src/Select.js

@@ -31,29 +31,6 @@ function stringifyValue (value) {
 	}
 }
 
-if (!Array.prototype.findIndex) {
-  Array.prototype.findIndex = function(predicate) {
-    if (this === null) {
-      throw new TypeError('Array.prototype.findIndex called on null or undefined');
-    }
-    if (typeof predicate !== 'function') {
-      throw new TypeError('predicate must be a function');
-    }
-    var list = Object(this);
-    var length = list.length >>> 0;
-    var thisArg = arguments[1];
-    var value;
-
-    for (var i = 0; i < length; i++) {
-      value = list[i];
-      if (predicate.call(thisArg, value, i, list)) {
-        return i;
-      }
-    }
-    return -1;
-  };
-}
-
 const stringOrNode = PropTypes.oneOfType([
 	PropTypes.string,
 	PropTypes.node
@@ -544,7 +521,7 @@ class Select extends React.Component {
 				focusedIndex: null
 			}, () => {
 				var valueArray = this.getValueArray(this.props.value);
-				if (valueArray.find(i => i[this.props.valueKey] === value[this.props.valueKey])) {
+				if (valueArray.some(i => i[this.props.valueKey] === value[this.props.valueKey])) {
 					this.removeValue(value);
 				} else {
 					this.addValue(value);

src/utils/defaultMenuRenderer.js

@@ -18,7 +18,7 @@ function menuRenderer ({
 	let Option = optionComponent;
 
 	return options.map((option, i) => {
-		let isSelected = valueArray && valueArray.findIndex(x => x[valueKey] == option[valueKey]) > -1;
+		let isSelected = valueArray && valueArray.some(x => x[valueKey] == option[valueKey]);
 		let isFocused = option === focusedOption;
 		let optionClass = classNames(optionClassName, {
 			'Select-option': true,