A, JSON vs JS objects

1, the difference

the difference	Javascript objects	Json
meaning	Instance of an object	A data format (serialization format)
transmission	Can not transfer	It can be cross-platform transmission, lightweight
format	1. bond without the quotes, and single and double quotation marks all rows 2 value may be a function, an object, a string, numeric, boolean, etc.	1. The key must have double quotes 2. The value can not function / undefined / NaN

NOTE: 序列化格式: There are early XML, javascript later based on the birth of more lightweight JSON, and then later there YAML.

For a large number of data sets for scientific use, such as climate, ocean models and satellite data to develop a specific binary serialization standards, such as HDF, netCDF and older GRIB.

2, the sequence of

(1) the sequence of operations

We are serialized - JSON.stringify()
Deserialization - JSON.parse(), (not recommended) eval ()

// 初始化 JS 对象
var obj_origin = {
    a: 1,
    b: "2",
    'c': 3
}
console.log(obj_origin) // { a: 1, b: '2', c: 3 }

// 正序列化
var objStr = JSON.stringify(obj_origin)
console.log(objStr) // {"a":1,"b":"2","c":3}

// 反序列化 
var obj = JSON.parse(objStr)
console.log(obj) // { a: 1, b: '2', c: 3 }

var obj2 = eval("(" + objStr + ")")
console.log(obj2) // { a: 1, b: '2', c: 3 }

（2）eval()

First, eval()the function may be a JS expression is evaluated to a specific object, so the object to parse the string into only one JS effect.

Question one: Why eval () to add parentheses around when parsing?

answer:

. 1, the object is started js "{}" and ending manner, but in the js, it will be mistaken for a block of statements (statement) to process.

2, so with parentheses, in order to put this into a string expression , rather than the statement to execute.

alert(eval("{}")); // return undefined

alert(eval("({})"));// return object[Object]

Question two: Why is not recommended to use eval () it?

answer:

Although the resolving power is stronger than JSON.parse eval, it can not resolve standard JSON string, but the above problem of an example can be seen, eval is unsafe , especially when the data is given to third parties. Therefore, it is recommended to use JSON.parse ( in fact eval JSON.parse bottom is called ).

二、JSON vs JSONB

For more see my previous blog post: Postgres the JSON / JSONB type

三、JSON vs JSONP

For more see my previous blog post: AJAX cross-domain in three ways

Object js / json / jsonb / jsonp difference