Passing function parameter not working?

Question

I want to pass a parameter to the function, but getting error

Cannot read property of undefined?"

var getNow= function(combo) 
{
var checkValue= Ext.ComponentQuery.query('combobox[name=combo]')[0];
checkValue.isVisible();
};

//call it using this:
getNow("comboBoxName");

Answer 1

Try

var checkValue= Ext.ComponentQuery.query('combobox[name=combo]')[0];

change to

var checkValue= Ext.ComponentQuery.query('combobox[name=' + combo + ']')[0];

Added snippet, it seems work, so you have to give further informations.

 var states = Ext.create('Ext.data.Store', { fields: ['abbr', 'name'], data : [ {"abbr":"AL", "name":"Alabama"}, {"abbr":"AK", "name":"Alaska"}, {"abbr":"AZ", "name":"Arizona"} ] }); Ext.create('Ext.form.ComboBox', { fieldLabel: 'Choose State', store: states, queryMode: 'local', valueField: 'abbr', name: "asd", renderTo: Ext.getBody(), // Template for the dropdown menu. // Note the use of the "x-list-plain" and "x-boundlist-item" class, // this is required to make the items selectable. tpl: Ext.create('Ext.XTemplate', '<ul class="x-list-plain"><tpl for=".">', '<li role="option" class="x-boundlist-item">{abbr} - {name}</li>', '</tpl></ul>' ), // template for the content inside text field displayTpl: Ext.create('Ext.XTemplate', '<tpl for=".">', '{abbr} - {name}', '</tpl>' ) }); var getNow= function(combo) { var checkValue= Ext.ComponentQuery.query('combobox[name=' + combo+ ']')[0]; console.log(checkValue.isVisible()); // It returns true or false, then what you want it to do? }; //call it using this: getNow("asd"); 

 <script src="https://cdnjs.cloudflare.com/ajax/libs/extjs/4.2.1/ext-all.min.js"></script> <link href="https://cdnjs.cloudflare.com/ajax/libs/extjs/4.2.1/resources/css/ext-all.css" rel="stylesheet"/> 

Unless you use Es6 with special string notation, javascript's string won't parse value for you, so the combo is unused here.