js对象2

/*
var obj = {
    "a" : 1
}
*/
// 获取数据
//console.log( obj.a );
//console.log( obj['a'] );

// 设置
//obj.a = 2;
//obj.b = 3;
//obj['c'] = 4;
//console.log( obj );

//var b = 'c';
//obj[b] = 5;
//console.log( obj );


/*
console.log( div1.style.color );
console.log( div1.style['color'] );
console.log( div1['style']['color'] );
*/


/*
var arr = ['a','b','c'];
//console.log( typeof(arr) );    // 'object'
for( var i in arr ){
    console.log( typeof(i), i );
}
*/


/*
var obj = {"a":1, "b":2, "i":3};
//console.log( obj[0] );
for( var i in obj ){
    //console.log( typeof(i), i, obj[i] );
    console.log( obj['i'] );
    //console.log( obj.i );
}
*/



// 判断数据是否为数组
//var obj = {"a":1, "b":2};
//var arr = ["a", "b", "c"];

//alert( typeof(obj) );    //'object'
//alert( typeof(arr) );    //'object'

//var b1 = Array.isArray(obj);
//var b2 = Array.isArray(arr);
//console.log( b1, b2 );

//console.log( obj.length, arr.length );

//arr instanceof Array 判断arr在其原型链中是否存在 Array 这个构造函数的 prototype 属性。
//var b = arr instanceof Array;
//console.log(b);



/*
//  判断某个属性在对象中是否存在
var obj = {
    a : 1,
    b : undefined
}

var b = 'a' in obj;
console.log( b );

//var b = obj['b'];
//console.log( b );
*/

/*
var obj = {
    a : 1
}
console.log( obj.a );
var r = delete obj.b;
console.log( obj.a );
console.log( r );
*/



//var arr = ["a", "b", "c", "a"];
// 某个成员在数组中是否存在
//var i = arr.indexOf("d");    
// 如果"a"在arr数组中存在，则返回"a"的下标，如果不存在，则返回-1
//console.log( i );
//console.log( arr )    //["a", "b", "c"]