asciichart.js

"use strict";

(function (exports) {

    exports.plot = function (series, cfg = undefined) {

        var toFixedTrailing = function(x, trailing = 2) {
            if (Math.abs(x) > 1) {
                var trailing = trailing || 0,
                    neg = x < 0,
                    power = Math.pow(10, trailing),
                    x = Math.round(x * power),
                    integral = String((neg ? Math.ceil : Math.floor)(x / power)),
                    fraction = String((neg ? -x : x) % power),
                    padding = new Array(Math.max(trailing - fraction.length, 0) + 1).join('0');

                return trailing ? integral + '.' +  padding + fraction : integral;
            } else {
                var numDigits = x !== 0 ? Math.ceil(Math.log10(Math.abs(x))) : 0;
                var rounded = Math.round(x*Math.pow(10,trailing-numDigits))*Math.pow(10,numDigits-trailing);
                return rounded.toFixed(Math.max(trailing-numDigits,0));
            }
        }


        let min = series[0]
        let max = series[0]

        let paddingLength = 0
        for (let i = 1; i < series.length; i++) {
            min = Math.min (min, series[i])
            max = Math.max (max, series[i])

            var numChars = String(toFixedTrailing(series[i])).length
            paddingLength = numChars > paddingLength ? numChars : paddingLength
        }

        let range   = Math.abs (max - min)
        cfg         = (typeof cfg !== 'undefined') ? cfg : {}
        let offset  = (typeof cfg.offset  !== 'undefined') ? cfg.offset  : 3
        let padding = (typeof cfg.padding !== 'undefined') ? cfg.padding : Array(paddingLength).fill(" ")
        let height  = (typeof cfg.height  !== 'undefined') ? cfg.height  : range
        let ratio   = height / range
        let min2    = Math.round (min * ratio)
        let max2    = Math.round (max * ratio)
        let rows    = Math.abs (max2 - min2)
        let width   = series.length + offset
        let format  = (typeof cfg.format !== 'undefined') ? cfg.format : function (x) {
            return (padding + toFixedTrailing(x)).slice (-padding.length)
        }

        let result = new Array (rows + 1) // empty space
        for (let i = 0; i <= rows; i++) {
            result[i] = new Array (width)
            for (let j = 0; j < width; j++) {
                result[i][j] = ' '
            }
        }

        for (let y = min2; y <= max2; ++y) { // axis + labels
            let label = format (max - (y - min2) * range / rows, y - min2)
            result[y - min2][Math.max (offset - label.length, 0)] = label
            result[y - min2][offset - 1] = (y == 0) ? '┼' : '┤' 
        }

        let y0 = Math.round (series[0] * ratio) - min2
        result[rows - y0][offset - 1] = '┼' // first value

        for (let x = 0; x < series.length - 1; x++) { // plot the line
            let y0 = Math.round (series[x + 0] * ratio) - min2
            let y1 = Math.round (series[x + 1] * ratio) - min2
            if (y0 == y1) {
                result[rows - y0][x + offset] = '─'
            } else {                        
                result[rows - y1][x + offset] = (y0 > y1) ? '╰' : '╭'
                result[rows - y0][x + offset] = (y0 > y1) ? '╮' : '╯'
                let from = Math.min (y0, y1)
                let to = Math.max (y0, y1)
                for (let y = from + 1; y < to; y++) {
                    result[rows - y][x + offset] = '│'
                }
            }
        }

        return result.map (function (x) { return x.join ('') }).join ('\n')
    }  

}) (typeof exports === 'undefined' ? /* istanbul ignore next */ this['asciichart'] = {} : exports);