note for "The Art of Readable Code" - CH9 Variables and Readability

減少不必要的變數可以增加閱讀性, 比如

root_message.last_view_time = datetime.datetime.now()
會比下面code更容易理解
now = datetime.datetime.now()
root_message.last_view_time = now

下面還有幾個需要優化的的例子, 可以好好思考如何改善.

boolean done = false;
while (/* condition */ && !done) {
    ...
    if (...) {
        done = true;
        continue;
    }
}
與
var remove_one = function (array, value_to_remove) {
    var index_to_remove = null;
    for (var i = 0; i < array.length; i += 1) {
        if (array[i] === value_to_remove) {
            index_to_remove = i;
            break;
        }
    }
    if (index_to_remove !== null) {
        array.splice(index_to_remove, 1); 
    }
};

programmer都知道要盡量限縮變數的範圍, 因為可視範圍小, 要記住的變數數量也會減少, 也且可以避免global/local variable用錯的窘境.

submitted = false; // Note: global variable
var submit_form = function (form_name) {
    if (submitted) {
        return;  // don't double-submit the form
    }
    ...
    submitted = true;
};
可以被修改成
var submit_form = (function () {
    var submitted = false; // Note: can only be accessed by the function below
    return function (form_name) {
        if (submitted) {
            return;  // don't double-submit the form
        }
        ...
        submitted = true; 
    };
}());

參考資料:
1. The Art of Readable Code