vant-weapp/packages/common/utils.ts

export function isDef(value: any): boolean {
  return value !== undefined && value !== null;
}

export function isObj(x: any): boolean {
  const type = typeof x;
  return x !== null && (type === 'object' || type === 'function');
}

export function isNumber(value) {
  return /^\d+$/.test(value);
}

export function range(num: number, min: number, max: number) {
  return Math.min(Math.max(num, min), max);
}

export function nextTick(fn: Function) {
  setTimeout(() => {
    fn();
  }, 1000 / 30);
}

let systemInfo: WechatMiniprogram.GetSystemInfoSuccessCallbackResult = null;
export function getSystemInfoSync() {
  if (systemInfo == null) {
    systemInfo = wx.getSystemInfoSync();
  }

  return systemInfo;
}

export function addUnit(value?: string | number): string | undefined {
  if (!isDef(value)) {
    return undefined;
  }

  value = String(value);
  return isNumber(value) ? `${value}px` : value;
}