This should be much faster

 li = '';
 $.each(data.result, function(){
     li += "<li>Name: " + this['name'] + "</li>" +
          "<li>Age: " + this['age'] + "</li>" +
          "<li>Company: "+this['company']+"</li>" +
          "<br />"; // could remove this and use css
 });

 $("ul").append(li);

See http://net.tutsplus.com/tutorials/javascript-ajax/10-ways-to-instantly-increase-your-jquery-performance/

ES6

As the first answer mentions, with ES6/Babel, you can now create multi-line strings simply by using backticks:

const htmlString = `Say hello to 
multi-line
strings!`;

Interpolating variables is a popular new feature that comes with back-tick delimited strings:

const htmlString = `${user.name} liked your post about strings`;

This just transpiles down to concatenation:

user.name + ' liked your post about strings'

ES5

Google's JavaScript style guide recommends to use string concatenation instead of escaping newlines:

Do not do this:

var myString = 'A rather long string of English text, an error message \

                actually that just keeps going and going -- an error \
                message to make the Energizer bunny blush (right through \
                those Schwarzenegger shades)! Where was I? Oh yes, \
                you\'ve got an error and all the extraneous whitespace is \
                just gravy.  Have a nice day.';

The whitespace at the beginning of each line can't be safely stripped at compile time; whitespace after the slash will result in tricky errors; and while most script engines support this, it is not part of ECMAScript.

Use string concatenation instead:

var myString = 'A rather long string of English text, an error message ' +

               'actually that just keeps going and going -- an error ' +
               'message to make the Energizer bunny blush (right through ' +
               'those Schwarzenegger shades)! Where was I? Oh yes, ' +
               'you\'ve got an error and all the extraneous whitespace is ' +
               'just gravy.  Have a nice day.';