Character frequency in order of appearance in JavaScript means counting how many times each character occurs while keeping their original sequence. It helps analyze string patterns and character distribution.
- Counts occurrences of each character in a string.
- Maintains the original order of appearance.
- Usually implemented using objects or maps.
- Useful in text analysis and string processing.
- Good practice for JavaScript logic building.
[Method 1]: Using Object
Object in JavaScript allow storing key value pairs. So we use items as keys and their frequencies as values.
function freqCount(s) {
const freq = {};
for (let x of s) {
freq[x] = (freq[x] || 0) + 1;
}
return freq;
}
// Example usage
console.log(freqCount("geeksforgeeks"));
[Method 2]: Using Map
JS Map also store key value pairs and works for data types other than string as well.
function freqCount(s) {
const m = new Map();
for (let x of s) {
m.set(x, (m.get(x) || 0) + 1);
}
return m;
}
// Example usage
console.log(freqCount("geeksforgeeks"));
[Method 3]: Using Regular Expression
If our input string contains mixed characters and we wish to find frequencies of only alphabetic characters, we can use regular expressions.
function freqCount(s) {
return (s.match(/[a-z]/gi) || []).reduce((freq, x) => {
freq[x] = (freq[x] || 0) + 1;
return freq;
}, {});
}
// Example usage
console.log(freqCount("geeksforgeeks"));