"usingComponents": {
  "van-field": "@vant/weapp/field/index"
}

<van-cell-group>
  <van-field
    value="{{ value }}"
    placeholder="请输入用户名"
    border="{{ false }}"
    bind:change="onChange"
  />
</van-cell-group>

Page({
  data: {
    value: '',
  },

  onChange(event) {
    // event.detail 为当前输入的值
    console.log(event.detail);
  },
});

<van-cell-group>
  <van-field
    model:value="{{ value }}"
    placeholder="请输入用户名"
    border="{{ false }}"
  />
</van-cell-group>

Page({
  data: {
    value: '',
  },
});

<van-cell-group>
  <van-field
    value="{{ username }}"
    required
    clearable
    label="用户名"
    icon="question-o"
    placeholder="请输入用户名"
    bind:click-icon="onClickIcon"
  />

  <van-field
    value="{{ password }}"
    type="password"
    label="密码"
    placeholder="请输入密码"
    required
    border="{{ false }}"
  />
</van-cell-group>

<van-cell-group>
  <van-field
    value="输入框已禁用"
    label="用户名"
    left-icon="contact"
    disabled
    border="{{ false }}"
  />
</van-cell-group>

<van-cell-group>
  <van-field
    value="{{ username }}"
    label="用户名"
    placeholder="请输入用户名"
    error
  />
  <van-field
    value="{{ phone }}"
    label="手机号"
    placeholder="请输入手机号"
    error-message="手机号格式错误"
    border="{{ false }}"
  />
</van-cell-group>

<van-cell-group>
  <van-field
    value="{{ username3 }}"
    label="用户名"
    placeholder="请输入用户名"
    input-align="right"
  />
</van-cell-group>

<van-cell-group>
  <van-field
    value="{{ message }}"
    label="留言"
    type="textarea"
    placeholder="请输入留言"
    autosize
    border="{{ false }}"
  />
</van-cell-group>

<van-cell-group>
  <van-field
    value="{{ sms }}"
    center
    clearable
    label="短信验证码"
    placeholder="请输入短信验证码"
    border="{{ false }}"
    use-button-slot
  >
    <van-button slot="button" size="small" type="primary">
      发送验证码
    </van-button>
  </van-field>
</van-cell-group>

<van-field
  value="{{ value }}"
  placeholder="请输入用户名"
  border="{{ false }}"
  clearable
  extra-event-params
  bind:change="onChange"
/>

Page({
  data: {
    value: '',
  },
  onChange(e) {
    const { value, callback } = e.detail;

    callback({
      value: value + 1,
      cursor: 0,
    });
  },
});