Can I use
?

let

- OTHER

Declares a variable with block level scope

IE

  1. 5.5 - 10: Not supported
  2. 11: Partial support

Edge

  1. 12 - 85: Supported
  2. 86: Supported

Firefox

  1. 2 - 43: Disabled by default
  2. 44 - 80: Supported
  3. 81: Supported
  4. 82 - 83: Supported

Chrome

  1. 4 - 18: Not supported
  2. 19 - 40: Disabled by default
  3. 41 - 48: Partial support
  4. 49 - 85: Supported
  5. 86: Supported
  6. 87 - 89: Supported

Safari

  1. 3.1 - 9.1: Not supported
  2. 10 - 10.1: Partial support
  3. 11 - 13.1: Supported
  4. 14: Supported
  5. TP: Supported

Opera

  1. 9 - 12.1: Not supported
  2. 15 - 27: Disabled by default
  3. 28 - 35: Partial support
  4. 36 - 70: Supported
  5. 71: Supported

iOS Safari

  1. 3.2 - 9.3: Not supported
  2. 10 - 10.3: Partial support
  3. 11 - 13.7: Supported
  4. 14: Supported

Opera Mini

  1. all: Not supported

Android Browser

  1. 2.1 - 4.4.4: Not supported
  2. 81: Supported

Blackberry Browser

  1. 7: Not supported
  2. 10: Not supported

Opera Mobile

  1. 10 - 12.1: Not supported
  2. 59: Supported

Chrome for Android

  1. 85: Supported

Firefox for Android

  1. 79: Supported

IE Mobile

  1. 10: Not supported
  2. 11: Supported

UC Browser for Android

  1. 12.12: Supported

Samsung Internet

  1. 4: Partial support
  2. 5 - 11.2: Supported
  3. 12.0: Supported

QQ Browser

  1. 10.4: Supported

Baidu Browser

  1. 7.12: Partial support

KaiOS Browser

  1. 2.5: Supported
Resources:
MDN Web Docs - let
Variables and Constants in ES6