You can wrap into a util function like that:
``` .javascript
function customIndexOf() {
  return 'quack'
}

function withCustomIndexOf(fun) {
  const oldIndexOf = Array.prototype.indexOf
  Array.prototype.indexOf = customIndexOf
  fun()
  Array.prototype.indexOf = oldIndexOf
}

withCustomIndexOf(() => {
  console.log([123].indexOf()) // quack
})

console.log([123].indexOf()) // -1
```

Note, it will only work with sync code, async code (callbacks, promises)
will ~probably~ be called after the reset of the prototype function
-- 
Augusto Moura
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You can wrap into a util function like that:
```js
function customIndexOf() {
  return 'quack'
}

function withCustomIndexOf(fun) {
  const oldIndexOf = Array.prototype.indexOf
  Array.prototype.indexOf = customIndexOf
  fun()
  Array.prototype.indexOf = oldIndexOf
}

withCustomIndexOf(() => {
  console.log([123].indexOf()) // quack
})

console.log([123].indexOf()) // -1
```

Note, it will only work with sync code, async code (callbacks, promises)
will ~probably~ be called after the reset of the prototype function

**Edit:** The problem with this solution is because it will actually change behavior down to the call stack, third party functions will have the behavior compromised
```js
withCustomIndexOf(() => {
  $('*').find('div') // may not work because will execute with the `customIndexOf` in Array.prototype instead of the default method
})
```

You can wrap into a util function like that:
```js
function customIndexOf() {
  return 'quack'
}

function withCustomIndexOf(fun) {
  const oldIndexOf = Array.prototype.indexOf
  Array.prototype.indexOf = customIndexOf
  fun()
  Array.prototype.indexOf = oldIndexOf
}

withCustomIndexOf(() => {
  console.log([123].indexOf()) // quack
})

console.log([123].indexOf()) // -1
```

Note, it will only work with sync code, async code (callbacks, promises)
will ~probably~ be called after the reset of the prototype function

**Edit:** The problem with this solution is because it will actually change behavior down to the call stack, third party functions will have the behavior compromised
```js
withCustomIndexOf(() => {
  $('*').find('div') // may not work because it's using the `customIndexOf` instead of the default method
})
```

You can wrap into a util function like that:
```js
function customIndexOf() {
  return 'quack'
}

function withCustomIndexOf(fun) {
  const oldIndexOf = Array.prototype.indexOf
  Array.prototype.indexOf = customIndexOf
  fun()
  Array.prototype.indexOf = oldIndexOf
}

withCustomIndexOf(() => {
  console.log([123].indexOf()) // quack
})

console.log([123].indexOf()) // -1
```

Note, it will only work with sync code, async code (callbacks, promises)
will ~probably~ be called after the reset of the prototype function

**Edit:** The problem with this solution is because it will actually change behavior down to the call stack, third party functions will have the behavior compromised```js
withCustomIndexOf(() => {
  $('*').find('div') // may not work because it's using the `customIndexOf` instead of the default method
})
```

You can wrap into a util function like that:
```js
function customIndexOf() {
  return 'quack'
}

function withCustomIndexOf(fun) {
  const oldIndexOf = Array.prototype.indexOf
  Array.prototype.indexOf = customIndexOf
  fun()
  Array.prototype.indexOf = oldIndexOf
}

withCustomIndexOf(() => {
  console.log([123].indexOf()) // quack
})

console.log([123].indexOf()) // -1
```

Note, it will only work with sync code, async code (callbacks, promises)
will ~probably~ be called after the reset of the prototype function

Edit: The problem with this solution is because it will actually change behavior down to the call stack, third party functions will have the behavior compromised
```js
withCustomIndexOf(() => {
  $('*').find('div') // may not work because it's using the `customIndexOf` instead of the default method
})
```

You can wrap into a util function like that:
```js
function customIndexOf() {
  return 'quack'
}

function withCustomIndexOf(fun) {
  const oldIndexOf = Array.prototype.indexOf
  Array.prototype.indexOf = customIndexOf
  fun()
  Array.prototype.indexOf = oldIndexOf
}

withCustomIndexOf(() => {
  console.log([123].indexOf()) // quack
})

console.log([123].indexOf()) // -1
```

Note, it will only work with sync code, async code (callbacks, promises)
will ~probably~ be called after the reset of the prototype function

You can wrap into a util function like that:
``` .js
function customIndexOf() {
  return 'quack'
}

function withCustomIndexOf(fun) {
  const oldIndexOf = Array.prototype.indexOf
  Array.prototype.indexOf = customIndexOf
  fun()
  Array.prototype.indexOf = oldIndexOf
}

withCustomIndexOf(() => {
  console.log([123].indexOf()) // quack
})

console.log([123].indexOf()) // -1
```

Note, it will only work with sync code, async code (callbacks, promises)
will ~probably~ be called after the reset of the prototype function

You can wrap into a util function like that:
``` .lang-javascript
function customIndexOf() {
  return 'quack'
}

function withCustomIndexOf(fun) {
  const oldIndexOf = Array.prototype.indexOf
  Array.prototype.indexOf = customIndexOf
  fun()
  Array.prototype.indexOf = oldIndexOf
}

withCustomIndexOf(() => {
  console.log([123].indexOf()) // quack
})

console.log([123].indexOf()) // -1
```

Note, it will only work with sync code, async code (callbacks, promises)
will ~probably~ be called after the reset of the prototype function