Teach you how to use charAt() in JavaScript to count the most frequently appearing characters and their number of occurrences

Previously, I introduced the use of the charAt() method in JavaScript. Today, I will share with you the example code of js to count the characters and times with the highest number of times. The specific content is as follows:

Determine the character that appears most frequently in a string 'aabcdobdackoppz' and count its number of occurrences

First we need to understand a knowledge point: (how to determine whether the object has this attribute)

// There is an object to determine whether it has this attribute // Writing method: object['attribute name']
    var o = {
        age : 18 ,
        sex : 'male'
    }
    if(o['sex']){
        console.log('This property exists');
    } else {
        console.log('No such property');
    }

Core algorithm:

1. We can use the charAt() method to traverse the string.

2. Store each character in the object. If the object does not have this attribute, assign it a value of 1. If the attribute exists, add 1.

3. Traverse the object and get the maximum value and number of occurrences.

1. Use the charAt method to traverse the array 'aabcdobdackoppz' (which can be understood as storing the value in the object obj)

<script>    
    var str = 'aabcdobdackoppz' ;
    var obj = {} ;
    for(var i = 0 ; i < str.length ; i++){
        var chars = str.charAt(i) // chars is each character of the string if(obj[chars]){ // o[chars] gets the attribute obj[chars]++
        } else {
            obj[chars] = 1 ;
        }
    }
    console.log(obj);
 
</script>

At this point, the value has been stored in the obj object.

2. Next, you just need to traverse the object to get the maximum value and number of occurrences

<script>
    //Traverse the object var max = 0;
    var ch = '';
    for (var k in obj) { // To traverse an object, you need to use for in
        // k gets the attribute name, obj[k] gets the attribute value // The attribute name k here is only useful in the loop, so we need to create a ch to store k
        if (obj[k] > max) {
            max = obj[k];
            ch = k;
        }
    }
    console.log(ch + 'The most frequent occurrence' + 'The number of occurrences is:' + max);
</script>

Summary: We can understand that all characters first execute obj[chars]=1, which is equivalent to creating an object, and then judging whether the object already exists.

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