src/string/append.js
function append(str, postfix) {
    if (!str && str !== 0) {
        str = '';
    } else {
        str = str.toString();
    }
    return str + postfix;
}
function append(str, postfix) {
    if (!str && str !== 0) {
        str = '';
    } else {
        str = str.toString();
    }
    return str + postfix;
}
function append ( str , postfix ) { if ( ! str && str !== 0 ) { str = '' ; } else { str = str . toString ( ) ; } return str + postfix ; }
Appends characters to a string.

{{ 'sky' | append '.jpg' }} => 'sky.jpg'
Appends characters to a string .