js点击切换文字

// javascript
var  a = document.getElementsByTagName( 'a' )[0]
a.addEventListener( 'click' , function (){
    if (a.innerText ==  '123' ){a.innerText =  '456' }
    else {a.innerText =  '123' }
}, false )

// jQuery
$( 'a' ).click( function (){
    if ($( this ).text() ==  '123' )
        {$( this ).text( '456' )}
    else
        {$( this ).text( '123' )}
})