Why I'm I getting "undefined is not a function" in the following ES6 for loop?

Question

The input:

first line

second line third line

fourth line

The code:

let res = str.split('\n\n')
for (let result of res) {
    res = `<p class="blockquote">${res.replace(/^> /gm, '')}</p>`
}
console.log(`text: ${res}`)

str.split('\n\n') outputs first line,second line third line,fourth line. What I expected.

Now I want to use the for loop to take each item and surround it with p tags. However, I get the following error:

TypeError: undefined is not a function

I'm not very experienced with ES6. Is there something wrong with the loop?

What are you trying to get in the end? an array of the four strings wrapped in the blockquote tags? can you show the desired output? — Touffy
– Touffy, Commented Oct 19, 2015 at 9:52

Touffy · Accepted Answer · 2015-10-19 09:39:35Z

3

Yes, there's something wrong. Two things.

res = `<p class="blockquote">${res.replace(/^> /gm, '')}</p>`

res is initially an array, so it has no replace method. That's the error you get.

The other thing, once you fix that (replace res with your loop variable result), is that you assign the resulting string to res. I'm not sure what you expect, but I guess it won't work that way.

answered Oct 19, 2015 at 9:39

Touffy

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3 Comments

loganfsmyth Over a year ago

Assigning to res is fine since it's only fetched one time at the start of the loop, though it is a little weird style-wise.

Touffy Over a year ago

@loganfsmyth I know it doesn't break the loop, but it overwrites each result so that in the end res only contains the last string, not all of them. I can only assume since OP hasn't clarified, but the most obviously desirable outcome would be to map each string to the string with tags.

loganfsmyth Over a year ago

Ah gotcha, my mistake then.

treeFan · Accepted Answer · 2019-01-03 07:27:43Z

3

The problem in assigning new value to res variable inside for loop. So after first loop step we will have another value in res and loop will end;

Try this code:

let str = 'first line\n\nsecond line third line\n\nfourth line';
let res = str.split('\n\n')

for (let result of res) {
    let i = `<p class="blockquote">${result.replace(/^> /gm, '')}</p>`
    console.log(i);
}

edited Jan 3, 2019 at 7:27

treeFan

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answered Oct 19, 2015 at 9:45

Yuriy Yakym

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1 Comment

loganfsmyth Over a year ago

Assigning to res is fine, though a little weird. It's just the .replace call that is wrong.

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