This search box in the header depends on jQueryUI's autocomplete and can be simply triggered by the following code:
new $.nd2Search({
placeholder : "Input Placeholder", // Placeholder in the search field
defaultIcon : "globe-alt", // optional: icon | null
source : [{ label : 'Displayed Value', value : 'real-value', icon : 'custom-icon'}], // autocomplete : option-source
fn : function(result) { // this function will be executed when a valid result item is selected
console.log('--- Your custom handling ---');
console.log('you picked: ');
console.log(result);
}
});