`“n”` can't run in `new Function()`

I want to run code dynamiclly, without using <script>，so I used new Function,but there is a problem when I write n :

<script>

new Function

n

function run (code) {
(new Function(code))()
}

run('console.log("run well")') // it work well
run('console.log("nError")') // error


the result is:
error

Uncaught SyntaxError: Invalid or unexpected token
at new Function (<anonymous>)
at run (<anonymous>:2:3)
at <anonymous>:1:1


And we can find the reason in console: the 'n' has been turn to a new line

(function() {
console.log(" // error here
Error")
})


so using ` to replace " can solve this problem:

run(`console.log("nWell")`)

(function() {
console.log(` // work here
Error`)
})


but it is not suitable that using ` in production, so if there other way to let it well done ?

new Function

3 Answers
3

Since the function body is a string, n will actually be converted to a newline character. You need to escape it by using \n.

n

\n

function run(code) {
(new Function(code))()
}

run('console.log("run well")') // it work well
run('console.log("\nError")') // error

This is because you forgot to escape the n as \n.

n

\n

You can re write your code as

function run (code) {
(new Function(code))()
}

run('console.log("run well")')
run('console.log("\nError")')


Console will be

run well

Error

Please try this you will get the output.

Note Below is the escaping chars in detail

JavaScript uses the (backslash) as an escape character for:1[2]

more details about escape characters

I suggest you better fix it in the function level than fix all the inputs to the function

You can modify your function to escape any n by str.replace

n

str.replace

function run(code) {
(new Function(code.replace(/n/g, "\n")))()
}


This will escape any number of occurrences for the n in code by \n.

n

code

\n

Hope this helps!

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