为什么此javascript函数针对同一查询返回两个不同的结果？

Question

What I'm trying to do:
I'm trying to calculate the distance between two words in a string (in our example, var someString = "one two three four five six seven" . As you can see in my code below, I convert the string to an array with the split() method, then call the function minDist() that calculates the distance between the words.

What's the problem:
As you can see in the code and my relevant comments, everything works as intended if I call the function using the string (or rather, the array, "one", "two", "three", "four", "five", "six", "seven" ) directly. The result is, as expected, 3 - which is the distance between "one" and "four" in this specific example.
However, as you can see, if I try to call the function using the array's variable, the result is null.
Why is that and how can I resolve this problem?

 var someString = "one two three four five six seven" var distanceCheck = someString.split(" "); console.log("distanceCheck",distanceCheck,"Quick test. As expected, the result is: one,two,three,four,five,six,seven") for (var i = 0; i < distanceCheck.length; i++) { distanceCheck[i] = '"' + distanceCheck[i] + '"'; } var list2b = distanceCheck.join(", "); console.log("list2b",list2b,'As expected, the result is: "one", "two", "three", "four", "five", "six", "seven"') var check0 = minDist(["one", "two", "three", "four", "five", "six", "seven"], "one", "four"); console.log("check0",check0,"Result is: 3") var check1 = minDist([list2b], "one", "four"); console.log("check1",check1,"Result is: null. WHY?") function minDist(words, wordA, wordB) { var wordAIndex = null; var wordBIndex = null; var minDinstance = null; for (var i = 0, length = words.length; i < length; i++) { if (words[i] === wordA) { wordAIndex = i; } if (words[i] === wordB) { wordBIndex = i; } if (wordAIndex !== null && wordBIndex !== null) { var distance = Math.abs(wordAIndex - wordBIndex); if (minDinstance === null || minDinstance > distance) { minDinstance = distance; } } } return minDinstance; } 

Answer 1

Because [list2b] is not what you expect.

It is an array with one string:

"\\"one\\", \\"two\\", \\"three\\", \\"four\\", \\"five\\", \\"six\\", \\"seven\\""

As you can see it additionally has extra quotes

Answer 2

Use this corrected snippet

In one you were sending an array of value in other you were sending a single value of array. 2nd mistake was appending "" after and before in the values; string values are already quoted in the array in js you need not add quotes.

I have corrected both of them and you can see both are returning 3.

I have corrected these lines

var check1 = minDist(distanceCheck, "one", "four");

and you can omit this loop

//for (var i = 0; i < distanceCheck.length; i++) {
  //distanceCheck[i] = '"' + distanceCheck[i] + '"';
//}

 var someString = "one two three four five six seven" var distanceCheck = someString.split(" "); console.log(distanceCheck, "Quick test. As expected, the result is: one,two,three,four,five,six,seven") //for (var i = 0; i < distanceCheck.length; i++) { //distanceCheck[i] = '"' + distanceCheck[i] + '"'; //} var list2b = distanceCheck.join(", "); console.log("list2b", list2b, 'As expected, the result is: "one", "two", "three", "four", "five", "six", "seven"') var check0 = minDist(["one", "two", "three", "four", "five", "six", "seven"], "one", "four"); console.log("check0", check0, "Result is: 3") var check1 = minDist(distanceCheck, "one", "four"); console.log("check1", check1, "Result is no longer null.") function minDist(words, wordA, wordB) { var wordAIndex = null; var wordBIndex = null; var minDinstance = null; for (var i = 0, length = words.length; i < length; i++) { if (words[i] === wordA) { wordAIndex = i; } if (words[i] === wordB) { wordBIndex = i; } if (wordAIndex !== null && wordBIndex !== null) { var distance = Math.abs(wordAIndex - wordBIndex); if (minDinstance === null || minDinstance > distance) { minDinstance = distance; } } } return minDinstance; } 

Answer 3

First, you do not need to add "" to a string if you pretend to use it as an array. Your function expects an array of strings, not a single string. In the snippet i show you a working version. Because you are using a string for the array, the way to go is to get it back to a real array with split(",") (Note that i got rid of the .join(",")).

 var someString = "one two three four five six seven" var distanceCheck = someString.split(" "); console.log("distanceCheck",distanceCheck,"Quick test. As expected, the result is: one,two,three,four,five,six,seven") for (var i = 0; i < distanceCheck.length; i++) { distanceCheck[i] = '' + distanceCheck[i] + ''; } var list2b = distanceCheck.join(); console.log("list2b",list2b,'As expected, the result is: "one", "two", "three", "four", "five", "six", "seven"') var check0 = minDist(["one", "two", "three", "four", "five", "six", "seven"], "one", "four"); console.log("check0",check0,"Result is: 3") var check1 = minDist(list2b.split(","), "one", "four"); console.log("check1",check1,"Result is: null. WHY?") function minDist(words, wordA, wordB) { var wordAIndex = null; var wordBIndex = null; var minDinstance = null; for (var i = 0, length = words.length; i < length; i++) { if (words[i] === wordA) { wordAIndex = i; } if (words[i] === wordB) { wordBIndex = i; } if (wordAIndex !== null && wordBIndex !== null) { var distance = Math.abs(wordAIndex - wordBIndex); if (minDinstance === null || minDinstance > distance) { minDinstance = distance; } } } return minDinstance; } 

Answer 4

This is because list2b is one string, and [list2b] is an array with only one value. If you remove the for loop and replace [list2b] with distanceCheck it should work.