We can achieve this using javascript or using jquery.Below methods demonstrate it.

Method 1: Use any JavaScript to include another js file.

Step 1: Add following function in your page.

function includeScript(url)
{    
    var head = document.getElementsByTagName('head')[0];
    var script = document.createElement('script');
    script.type = 'text/javascript';
    script.src = url;
    head.appendChild(script);
}

Step 2: Now call the below includeScript function, Where you want to include the js file .

includeScript('/js/jquery-1.7.min.js');

Other method is:-

Method 2: Use jQuery to include another js file .

Step 1: Add jQuery File in your webpage like this.

<script src="//code.jquery.com/jquery-1.11.2.min.js"></script>

Step 2: Just call the includeScript function like below code.

 jQuery(document).ready(function(){
    $.includeScript('/js/jquery-1.7.min.js');
});