typeof does not work in vue

Using typeof to check variable types in Vue may fail because Vue's reactive system proxies variables. Solutions include: 1. Use Vue.util.typeCheck; 2. Use Object.prototype.toString.call(myVariable); 3. Use Babel's transform-typeof-symbol plug-in.

typeof is invalid in Vue

In Vue.js, use the typeof operator Checking the type of a variable may not work because Vue's unique reactive system proxies variables.

Cause:

When a variable is reactively proxied, it is replaced by a wrapper object. This wrapper object hijacks access to the variable, allowing it to automatically trigger updates when the value changes.

Solution:

In order to correctly check the type of a variable in Vue, you can use one of the following methods:

• Using Vue.util.typeCheck:

import { typeCheck } from 'vue/types/util'
typeCheck(myVariable) === 'Object' // true

• Using Object.prototype.toString.call(myVariable):

Object.prototype.toString.call(myVariable) === '[object Object]' // true

• Use Babel’s transform-typeof-symbol plugin:

This plugin will Compile the typeof operator into a more reliable alternative. Please refer to the Babel documentation for specific usage.

Note:

• ##Vue.util.typeCheck can only check basic types (such as Object, Array and String).
• Object.prototype.toString.call(myVariable) Can check a wider range of types, including Vue-specific types.
Babel’s
• transform-typeof-symbol plugin needs to be enabled in the Babel configuration.

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