Calculate the average status length in current Fanfou page

average_status_length.js

/**
 * What's the average status length in current Fanfou page?
 * Author: @kavinyao
 * MIT-licensed.
 */
(function(document) {
    function map(op, seq) {
        var result = []
        for(var i = 0;i < seq.length;i++)
            result.push(op(seq[i]))
        return result
    }

    function reduce(op, seq, initial) {
        var result = initial
        for(var i = 0;i < seq.length;i++)
            result = op(result, seq[i])
        return result
    }
    
    function average(seq) {
        return reduce(function(x, y) {
            return x+y
        }, seq, 0.0) / seq.length
    }

    var spans = document.getElementsByClassName('content')
    var lengths = map(function(s) {
        return s.textContent.length
    }, spans)

    console.log(average(lengths))
})(document)