JavaScript中的內定物件與函式: arguments, callee, caller, this, apply(), call()

function sum() {
    var total = 0;
    for( var i=0; i<arguments.length; i++ ) {
        total += arguments[i];
    }
    return total;
}

// 測試
log( sum() );                              // 結果 = 0
log( sum(1, 2) );                          // 結果 = 3
log( sum(1, 2, 3, 4, 5, 6, 7, 8, 9, 10) ); // 結果 = 55

function introduce() {
    var callback = null;
    var msg = ‘‘;
    for( var i=0; i<arguments.length; i++ ) {
        var p = arguments[i];
        if( typeof p == ‘string‘ ) {
            msg += ‘我叫‘+p;
        } else if( typeof p == ‘number‘ ) {
            msg += ‘今年‘+p+‘歲‘;
        } else if( typeof p == ‘function‘ ) {
            callback = p;
        }
    }

    if( callback != null ) {
        callback(msg);
    } else {
        log( msg );
    }
}

// 測試2
introduce(‘David‘);                    // console印出"我叫David"
introduce(‘David‘, 29);                // console印出"我叫David今年29歲"
introduce(‘David‘, function(msg) {     // 跳出"我叫David"的訊息
    alert(msg);
});
introduce(‘David‘, 29, function(msg) { // 跳出"我叫David今年29歲"的訊息
    alert(msg);
});

function methodA(p1, p2, p3) {
    log(‘========================‘);
    log( arguments ); // 實際傳入的參數陣列
    log( arguments.callee ); // 指到methodA
    log( arguments.callee.caller ); // 指到call methodA的object
    log( ‘宣告參數長度: ‘+arguments.callee.length );
    log( ‘實際參數長度: ‘+arguments.length );
    log( this );
    log( p1 );
    log( p2 );
    log( p3 );
}

function handleCaller() {
    methodA(‘xxx‘, ‘yyy‘);
    methodA.apply(handleCaller, [‘xxx‘, ‘yyy‘]); // 指定this object
}

function init() {
    handleCaller();
    methodA.call(handleCaller, ‘xxx‘, ‘yyy‘); // 指定this object
}
init();

function log(msg) {
    if( window.console ) {
        console.log(msg);
    }
}