How to find count matches in string with a regexp and variable, javascript

Hello I need to get the number of matches for each character in a string and I am trying to use “for” and RegEx but my code doesn’t work because I don’t know how to use variables in RegEx

let foo = (str) => {
  for(let i=0; i< str.length; i++){
  console.log((str.match(/{HERE MUST BE str[i]}/g) || []).length);
  }
};

foo('Wabba');

Answer

You can create regular expressions with variables by using RegExp:

...
var regexp = new RegExp(str[i], 'g');
console.log(str.match(regexp).length);
...

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