Function extend

test/tooltipTestHelper.js:27–34

(target, source)

}

function extend(target, source) {
    for (var key in source) {
        if (source.hasOwnProperty(key)) {
            target[key] = source[key];
        }
    }
    return target;
}

function makeCategoryData(scale, catePrefix, dataCount) {
    var categoryData = [];