dist/claygl.es.js
function (target, source) {
        if (source) {
            for (var propName in source) {
                if (target[propName] === undefined) {
                    target[propName] = source[propName];
                }
            }
        }
        return target;
    }
function (target, source) {
        if (source) {
            for (var propName in source) {
                if (target[propName] === undefined) {
                    target[propName] = source[propName];
                }
            }
        }
        return target;
    }
function ( target , source ) { if ( source ) { for ( var propName in source ) { if ( target [ propName ] === undefined ) { target [ propName ] = source [ propName ] ; } } } return target ; }
Extend properties to target if not exist.
@param  {Object} target
@param  {Object} source
@return {Object}
@memberOf clay.core.util
Extend properties to target if not exist .