RGB渐变算法（JavaScript）

        let begin = [252, 0, 255];
        let end = [0, 219, 222];
        let rgbArr = [];
        let length = this.geojsons.length;
        let r = begin[0] - ((begin[0] - end[0]) * data.rownum) / length;
        let g = begin[1] - ((begin[1] - end[1]) * data.rownum) / length;
        let b = begin[2] - ((begin[2] - end[2]) * data.rownum) / length;
        let rgb = "rgb(" + r + "," + g + "," + b + ")";

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data.rownum 指当前元素的位置