计算文本区域中的特定字符

Question

Other questions have been asked concerning word count in text areas, but they are not duplicates of this question:

What I am trying to do is write a JavaScript/jQuery function is called on the user clicking on a button. The function takes the value of a textarea and checks all the characters that are in there. And then check whether two characters have the same amount of occurrences. In the function I need to use an if-else statement.

Example: If the input has 3x [ and 3x ] : if (a.length == b.length) {} ( = true )

If the input has 3x [ and 2x ] : if (a.length == b.length) {} ( = false )

But I am not quite sure how I can count individual characters. I am guessing with some regex and a match , but the following does not seem to work:

var a = str.match(/\[+ /g),
    b = str.match(/\[+ /g);

if (a.length == b.length) {
    //do something
}

Here is a fiddle . As you can see, the count is not correct.

Answer 1

How about:

'a[b][ca[]de'.match(/\[/g).length;

output:

3

as expected.

Answer 2

var str =  'What I am trying to do is write a JavaScript/jQuery function is called on the user clicking on a button. The function takes the value of a textarea and checks all the characters that are in there. And then check whether two characters have the same amount of occurrences. In the function I need to use an if-else statement.'

var matchFrequency = function(a,b, text) {
    return text.split(a).length == text.split(b).length
}
matchFrequency('a','a',str)
//true
matchFrequency('a','b',str)
//false

Edit

var str = 'Hello [ Here are ] some random [ characters ]] And I need to [ count [ and ]'
matchFrequency('[',']',str)
//output - true

Answer 3

Would this work to you?

var aOccurrences = str.split("a").length - 1,
    bOccurrences = str.split("b").length - 1;

if(aOccurrences === bOccurrences) {
   //doSomething
}

DEMO

Answer 4

Make an array which is indexed with 'a' to 'z'.

For example:

var arr=[];

initialize the array with 0. I am giving code snippet here, I guess you can convert it into Javascript

for(i=0; i<='z'-'a';i++) // 'z'-'a' means ASCII value of 'z' minus ASCII value of 'a'
arr[i] = 0;

string text_area = the text area from input

for(i =0; i<text_area.length ; i++) //text_area.length = length of your text area
if(text_area[i]>='a'&&text_area[i]<='z') // considering only lower case letters for now   
arr[text_area[i]-'a'] = arr[text_area[i]-'a'] + 1; //if a character is found,add 1 to count

We have our arr[] ready. Now if we want to check if number of character 'C1' is equal to number of character 'C2', we need to check like this

if(arr['C1'-'a']==arr['C2'-'a']) 

Hope this will help.

Answer 5

My answer is only partially, since I don't know how to handle regex under javascript/JQuery. I will write it in java. If you match each occurence of a and b, you can compare both :

Pattern pa=Pattern.compile("a");
Matcher ma=pa.match(str);
Pattern pb=Pattern.compile("b");
Matcher mb=pb.match(str);
int counta=0;
int countb=0;
while(ma.find())
counta++;
while(mb.find())
countb++;
boolean result=counta==countb;

This is an idea of the structure. Hope it helps.