Mobile Platform as a Service:Data type

SJS supports the following data types:

• String: String
• Boolean: Boolean
• Number: Number
• Object: Object
• Function: Function
• Array: Array
• Date: Date
• Regexp: Regular expression

Obtain the data type

SJS provides constructor and typeof for you to obtain the data type.

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

// A 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 is either true or false.

Syntax

const a = true;

Attribute

• constructor: returns "Boolean".

Method

• toString
• valueOf

Object

Syntax

var o = {}; // Generate an empty object.
// Generate an object that is not empty.
o = {
  'str': "str", // The key of the object can be a string.
  constVar: 2, // The key of the object can also be an identifier that complies with variable definition rules.
  val: {}, // The value of the object can be of any data type.
};
// Read the attributes of the object.
console.log(1 === o['string']);
console.log(2 === o.constVar);
// Write the attributes of the object.
o['string']++;
o['string'] += 10;
o.constVar++;
o.constVar += 10;
// Read the attributes of the object.
console.log(12 === o['string']);
console.log(13 === o.constVar);

ES6 syntax:

// ES6 syntax is supported.
let a = 2;
o = { 
  a, // The attributes of the object.
  b() {}, // The method of the object.
};
const { a, b, c: d, e = 'default'} = {a: 1, b: 2, c: 3}; // Destructure an object and assign default values.
const {a, ...other} = {a: 1, b: 2, c: 3}; // Destructure an object and assign values.
const f = {...others}; // Destructure an object.

Attribute

constructor: returns "Object".

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

Method

toString: returns the string "[object Object]".

Function

Syntax

// Method 1: Declare a function
function a (x) {
  return x;
}
// Method 2: Specify an expression for the function
var b = function (x) {
  return x;
};
// Method 3: Create an arrow function
const double = x => x * 2;
function f(x = 2){} // Default function parameters.
function g({name: n = 'xiaoming', ...other} = {}) {} // Destructure function parameters and assign values.
function h([a, b] = []) {} // Destructure function parameters and assign values.
// Create an anonymous function and a closure
var c = function (x) {
  return function () { return x;}
};
var d = c(25);
console.log(25 === d());

You can use the arguments keyword in 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 in a function.

Method

toString: returns a string in the "[function Function]" format.

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 = []; // An empty array.
a = [5,"5",{},function(){}]; // An array that is not empty. The elements in the array can be of any data type.
const [b, , c, d = 5] = [1,2,3]; // Destructure an array and assign default values.
const [e, ...other] = [1,2,3]; // Destructure an array and assign values.
const f = [...other]; // Destructure an array.

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

To generate a date object, use getDate function. The function returns a date object whose value is the current time.

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

Field

• milliseconds: returns the number of milliseconds elapsed since January 1, 1970 00:00:00 UTC.
• datestring: returns a string in the month day, year hours:minutes:seconds format.

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(); // Return a date object whose value is 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

Call getRegExp function to generate a regexp object.

getRegExp(pattern[, flags])

Field

• pattern: content of regular expression.
• flags: modifying signs. The flags can only contain the following characters:
  • g: global
  • i: ignoreCase
  • m: multiline

Attribute

• constructor: returns the string "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);