# Data binding

The dynamic data in WXML comes from the data corresponding to the Page.

# Simple binding

Data binding wraps variables using Mustache syntax (double braces) and can act on:

# content

<view> {{ message }} </view>

Page({
  data: {
    message: 'Hello MINA!'
  }
})

# Component properties (required in double quotation marks)

<view id="item-{{id}}"> </view>

Page({
  data: {
    id: 0
  }
})

# Control properties (required in double quotes)

<view wx:if="{{condition}}"> </view>

Page({
  data: {
    condition: true
  }
})

# Keywords (required in double quotation marks)

True: Boolean type true, representing the truth value.

False: Boolean type false, representing the false value.

<checkbox checked="{{false}}"> </checkbox>

Special note: Don't writechecked = "false",The result is a character string that is converted to a boolean to represent the true value.

# operation

Simple operations can be performed within{{}}in the following ways:

# ternary operator

<view hidden="{{flag ? true : false}}"> Hidden </view>

# Arithmetic operations

<view> {{a + b}} + {{c}} + d </view>

Page({
  data: {
    a: 1,
    b: 2,
    c: 3
  }
})

The content in view is3 + 3 + d.

# Logical judgment

<view wx:if="{{length > 5}}"> </view>

# Character string operation

<view>{{"hello" + name}}</view>

Page({
  data:{
    name: 'MINA'
  }
})

# Data Path Computing

<view>{{object.key}} {{array[0]}}</view>

Page({
  data: {
    object: {
      key: 'Hello '
    },
    array: ['MINA']
  }
})

# combination

You can also directly combine in Mustache to form a new object or array.

# array

<view wx:for="{{[zero, 1, 2, 3, 4]}}"> {{item}} </view>

Page({
  data: {
    zero: 0
  }
})

Finally combined into an array[0, 1, 2, 3, 4].

# object

<template is="objectCombine" data="{{foo: a, bar: b}}"></template>

Page({
  data: {
    a: 1,
    b: 2
  }
})

The final object is{foo: 1, bar: 2}

You can also use the extension operator...to expand an object

<template is="objectCombine" data="{{...obj1, ...obj2, e: 5}}"></template>

Page({
  data: {
    obj1: {
      a: 1,
      b: 2
    },
    obj2: {
      c: 3,
      d: 4
    }
  }
})

The final composition is{a: 1, b: 2, c: 3, d: 4, e: 5}.

If the key and value of the object are the same, it can also be expressed indirectly.

<template is="objectCombine" data="{{foo, bar}}"></template>

Page({
  data: {
    foo: 'my-foo',
    bar: 'my-bar'
  }
})

The final object is{foo: 'my-foo', bar: 'my-bar'}.

Note : The above methods can be combined arbitrarily, but if there is a case of the same variable name, the latter will override the former, such as:

<template is="objectCombine" data="{{...obj1, ...obj2, a, c: 6}}"></template>

Page({
  data: {
    obj1: {
      a: 1,
      b: 2
    },
    obj2: {
      b: 3,
      c: 4
    },
    a: 5
  }
})

The final combination is{a: 5, b: 3, c: 6}.

Note: A space between curly braces and quotes will eventually resolve to a character string

<view wx:for="{{[1,2,3]}} ">
  {{item}}
</view>

It's equivalent to

<view wx:for="{{[1,2,3] + ' '}}">
  {{item}}
</view>