# Yahoo! UI Library

### tabview

Yahoo! UI Library > tabview > Lang.js (source view)

    (function() {

        YAHOO.util.Lang = {
            isArray: function(val) { // frames lose type, so test constructor string
                if (val.constructor && val.constructor.toString().indexOf('Array') > -1) {
                    return true;
                } else {
                    return YAHOO.util.Lang.isObject(val) && val.constructor == Array;
                }
            },

            isBoolean: function(val) {
                return typeof val == 'boolean';
            },

            isFunction: function(val) {
                return typeof val == 'function';
            },

            isNull: function(val) {
                return val === null;
            },

            isNumber: function(val) {
                return !isNaN(val);
            },

            isObject: function(val) {
                return typeof val == 'object' || YAHOO.util.Lang.isFunction(val);
            },

            isString: function(val) {
                return typeof val == 'string';
            },

            isUndefined: function(val) {
                return typeof val == 'undefined';
            }
        };
    })();

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