1# Checking a Key (ArkTS)
2
3
4Check whether a key exists.
5
6
7## How to Develop
8
91. Set the key alias (**keyAlias**), which cannot exceed 128 bytes.
10
112. Initialize the key property set. You can specify [HuksTag](../../reference/apis-universal-keystore-kit/js-apis-huks.md#hukstag) of the key to check. To check a single key, leave this parameter empty.
12
133. Use [hasKeyItem](../../reference/apis-universal-keystore-kit/js-apis-huks.md#hukshaskeyitem11) to check whether the key exists.
14
15```ts
16import { huks } from '@kit.UniversalKeystoreKit';
17
18/* 1. Set the key alias. */
19let keyAlias = 'test_key';
20let isKeyExist: Boolean;
21/* 2. Construct an empty object. */
22let huksOptions: huks.HuksOptions = {
23  properties: []
24}
25try {
26  /* 3. Check whether the key exists. */
27  huks.hasKeyItem(keyAlias, huksOptions, (error, data) => {
28    if (error) {
29      console.error(`callback: hasKeyItem failed, ` + JSON.stringify(error));
30    } else {
31      if (data !== null && data.valueOf() !== null) {
32        isKeyExist = data.valueOf();
33        console.info(`callback: hasKeyItem success, isKeyExist = ${isKeyExist}`);
34      }
35    }
36  });
37} catch (error) {
38  console.error(`callback: hasKeyItem input arg invalid, ` + JSON.stringify(error));
39}
40```
41