Mobile Platform as a Service:Data type

SJS supports the following data types:

• String: string

• Boolean: A Boolean value (true or false).

• Number: A numeric value.

• Object: object

• Function: function

• Array: array

• Date: Date

• Regexp (regular expression)

Determine the data type

SJS provides two ways to determine the data type: constructor and typeof.

constructor

const number = 10;
console.log(number.constructor); // "Number"
const string = "str";
console.log(string.constructor); // "String"
const boolean = true;
console.log(boolean.constructor); // "Boolean"
const object = {};
console.log(object.constructor); // "Object"
const func = function(){};
console.log(func.constructor); // "Function"
const array = [];
console.log(array.constructor); // "Array"
const date = getDate();
console.log(date.constructor); // "Date"
const regexp = getRegExp();
console.log(regexp.constructor); // "RegExp"

typeof

const num = 100;
const bool = false;
const obj = {};
const func = function(){};
const array = [];
const date = getDate();
const regexp = getRegExp();
console.log(typeof num); // 'number'
console.log(typeof bool); // 'boolean'
console.log(typeof obj); // 'object'
console.log(typeof func); // 'function'
console.log(typeof array); // 'object'
console.log(typeof date); // 'object'
console.log(typeof regexp); // 'object'
console.log(typeof undefined); // 'undefined'
console.log(typeof null); // 'object'

String

Syntax

'hello alipay';
"hello taobao";

ES6 syntax

// String template
const a = 'hello';
const str = `${a} alipay`;

Attribute

• constructor: Returns "String".

• length

Method

• toString

• valueOf

• charAt

• charCodeAt

• concat

• indexOf

• lastIndexOf

• localeCompare

• match

• replace

• search

• slice

• split

• substring

• toLowerCase

• toLocaleLowerCase

• toUpperCase

• toLocaleUpperCase

• trim

Number

Syntax

const num = 10;
const PI = 3.141592653589793;

Attribute

constructor: Returns "Number".

Method

• toString

• toLocaleString

• valueOf

• toFixed

• toExponential

• toPrecision

Boolean

A Boolean value can only be one of two specific values: true or false.

Syntax

const a = true;

Attribute

• constructor: Returns "Boolean".

Method

• toString

• valueOf

Object

Syntax

var o = {}; // Create a new empty object
// Create a new non-empty object
o = {
  'str': "str",  // The key of an object can be a string
  constVar: 2,  // The key of an object can also be an identifier that follows variable naming rules
  val: {}, // The value of an object can be of any type
};
// Read an object attribute
console.log(1 === o['string']);
console.log(2 === o.constVar);
// Write to an object attribute
o['string']++;
o['string'] += 10;
o.constVar++;
o.constVar += 10;
// Read an object attribute
console.log(12 === o['string']);
console.log(13 === o.constVar);

ES6 syntax:

// Supported
let a = 2;
o = { 
  a, // Object attribute
  b() {}, // Object method
};
const { a, b, c: d, e = 'default'} = {a: 1, b: 2, c: 3}; // Object destructuring assignment & default
const {a, ...other} = {a: 1, b: 2, c: 3}; // Object destructuring assignment
const f = {...others}; // Object destructuring

Attribute

constructor: Returns "Object".

console.log("Object" === {a:2,b:"5"}.constructor);

Method

toString: Returns "[object Object]".

Function

Syntax

// Method 1: Function declaration
function a (x) {
  return x;
}
// Method 2: Function expression
var b = function (x) {
  return x;
};
// Method 3: Arrow function
const double = x => x * 2;
function f(x = 2){} // Default function parameter
function g({name: n = 'xiaoming', ...other} = {}) {} // Destructuring assignment for function parameters
function h([a, b] = []) {} // Destructuring assignment for function parameters
// Anonymous function, closure
var c = function (x) {
  return function () { return x;}
};
var d = c(25);
console.log(25 === d());

The arguments keyword is available within a function.

var a = function(){
    console.log(2 === arguments.length);
    console.log(1 === arguments[0]);
    console.log(2 === arguments[1]);
};
a(1,2);

Output:

true
true
true

Attribute

• constructor: Returns "Function".

• length: Returns the number of formal parameters of the function.

Method

toString: Returns "[function Function]".

Example

var f = function (a,b) { }
console.log("Function" === f.constructor);
console.log("[function Function]" === f.toString());
console.log(2 === f.length);

Output:

true
true
true

Array

Syntax

var a = [];      // Empty array
a = [5,"5",{},function(){}];  // Non-empty array. Array elements can be of any type.
const [b, , c, d = 5] = [1,2,3]; // Array destructuring assignment & default value
const [e, ...other] = [1,2,3]; // Array destructuring assignment
const f = [...other]; // Array destructuring

Attribute

• constructor: Returns "Array".

• length

Method

• toString

• concat

• join

• pop

• push

• reverse

• shift

• slice

• sort

• splice

• unshift

• indexOf

• lastIndexOf

• every

• some

• forEach

• map

• filter

• reduce

• reduceRight

Date

Syntax

You can use the getDate function to create a Date object. When called without arguments, the function returns an object that represents the current time.

getDate()
getDate(milliseconds)
getDate(datestring)
getDate(year, month[, date[, hours[, minutes[, seconds[, milliseconds]]]]])

Parameters

• milliseconds: The number of milliseconds that have elapsed since 00:00:00 Coordinated Universal Time (UTC) on January 1, 1970.

• datestring: A date string in the format "Month Day, Year Hours:Minutes:Seconds".

Attribute

constructor: Returns "Date".

Method

• toString

• toDateString

• toTimeString

• toLocaleString

• toLocaleDateString

• toLocaleTimeString

• valueOf

• getTime

• getFullYear

• getUTCFullYear

• getMonth

• getUTCMonth

• getDate

• getUTCDate

• getDay

• getUTCDay

• getHours

• getUTCHours

• getMinutes

• getUTCMinutes

• getSeconds

• getUTCSeconds

• getMilliseconds

• getUTCMilliseconds

• getTimezoneOffset

• setTime

• setMilliseconds

• setUTCMilliseconds

• setSeconds

• setUTCSeconds

• setMinutes

• setUTCMinutes

• setHours

• setUTCHours

• setDate

• setUTCDate

• setMonth

• setUTCMonth

• setFullYear

• setUTCFullYear

• toUTCString

• toISOString

• toJSON

Example

let date = getDate(); // Returns an object for the current time
date = getDate(1500000000000);
// Fri Jul 14 2017 10:40:00 GMT+0800 (China Standard Time)
date = getDate('2016-6-29');
// Fri June 29 2016 00:00:00 GMT+0800 (China Standard Time)
date = getDate(2017, 6, 14, 10, 40, 0, 0);
// Fri Jul 14 2017 10:40:00 GMT+0800 (China Standard Time)

Regexp

Syntax

You can use the getRegExp function to create a Regexp object.

getRegExp(pattern[, flags])

Parameters

• pattern: The text of the regular expression.

• flags: Modifiers. The value is a string that can contain any of the following characters:

  • g: global

  • i: ignoreCase

  • m: multiline

Attribute

• constructor: Returns "RegExp".

• global

• ignoreCase

• lastIndex

• multiline

• source

Method

• exec

• test

• toString

Example

var reg = getRegExp("name", "img");
console.log("name" === reg.source);
console.log(true === reg.global);
console.log(true === reg.ignoreCase);
console.log(true === reg.multiline);