semi-space copy allocation failed, javascript heap out of memory

Question

I was wondering why the below code returns a memory allocation error?

var countValidWords = function(sentence) {
    let words = [];
    for(let i = 0; i < sentence.length; ++i){
        let word = '';
        while(sentence[i] !== ' '){
            word += sentence[i];
            ++i;
        }
        if(word !== '')
            words.push(word);
    }
    console.log(words);
};

I'm simply trying to build an array of words from the inputted sentence (words can be separated by more than one space).

Answer 1

If the sentence doesn't end with a space, the while loop never ends, because it doesn't check if it has gone past the end of the string. As a result, you go into an infinite loop appending undefined to word , until you run out of memory.

Add a check that i is within the string length there.

 var countValidWords = function(sentence) { let words = []; for(let i = 0; i < sentence.length; ++i){ let word = ''; while(i < sentence.length && sentence[i] !== ' '){ word += sentence[i]; ++i; } if(word !== '') words.push(word); } console.log(words); };

Answer 2

while 子句需要检查i是否越界：

while(i < sentence.length && sentence[i] !== ' ')

Answer 3

How about this? It's not the most optimized version you might find but it works. You had an infinite loop on the while.

var countValidWords = function(sentence) {
    let words = [];
    let word = ''
    for(let i = 0; i < sentence.length; ++i){
        if(sentence[i] != '' && sentence[i] != ' '){
          word += sentence[i];
        }
        if(sentence[i] == ' ' || sentence[i + 1] === undefined){
          words.push(word);
          word = '';
        }
    }
    console.log(words);
};