离子 - 检查 Typescript 中的“”

Question

I am quite new to Ionic and Typescript and have received a defect of an application where a shell of an order is appearing but the data is all blank. My code:

// Loop over MONITORS
this.monitorArrayLength = this.detail.orderDetailList[i].monitors.length;
for (let j = 0; j < this.monitorArrayLength; j++) {
  this.monitorArray[j] = this.detail.orderDetailList[i].monitors[j];

  if (
    this.monitorArray[j].serialNum !== null ||
    this.monitorArray[j].serialNum !== "" ||
    this.monitorArray[j].status !== null ||
    this.monitorArray[j].status !== "" ||
    this.monitorArray[j].brandModel !== null ||
    this.monitorArray[j].brandModel !== "" ||
    this.monitorArray[j].docId !== null ||
    this.monitorArray[j].docId !== ""
  ) {
    this.showMonitorArray[j] = true; // Show monitor

    if (this.monitorArray[j].docId !== null) {
      this.pdfIconArray[j] = true; // Show pdf icon
    } else {
      this.pdfIconArray[j] = false; // Show normal icon
    }
  } else {
    this.showMonitorArray[j] = false; // Don't show monitor
  }
}

So, basically nothing should appear if the results brought back from the database are null or "".

Here is the results I get back from the database:

monitors: [{ serialNum: "", status: "", brandModel: "", docId: null }]

The code that I have above is not checking correctly for the "" and the shell of the data is still displaying when it shouldn't be.

Is this the right syntax to check for ""?

Any help would be appreciated!

Answer 1

This has nothing to do with Ionic or TypeScript. You should change your if condition to say

serialNum is defined AND status is defined AND brandModel is defined AND docId is defined

where "defined" means not null or "" .

if (
  (this.monitorArray[j].serialNum !== null &&
    this.monitorArray[j].serialNum !== "") &&
  (this.monitorArray[j].status !== null &&
    this.monitorArray[j].status !== "") &&
  (this.monitorArray[j].brandModel !== null &&
    this.monitorArray[j].brandModel !== "") &&
  (this.monitorArray[j].docId !== null && this.monitorArray[j].docId !== "")
) {
  //...
}

But it looks really messy. You could shorten it to a function

function isDefined(monitor) {
  const { serialNum, status, brandModel, docId } = monitor;
  return serialNum && status && brandModel && docId;
}

which makes sure all these values are not falsy .