一、经纬度坐标转墨卡托坐标

var LLBAND = [75, 60, 45, 30, 15, 0]
var LL2MC = [
    [-0.0015702102444, 111320.7020616939, 1704480524535203, -10338987376042340, 26112667856603880, -35149669176653700, 26595700718403920, -10725012454188240, 1800819912950474, 82.5],
    [0.0008277824516172526, 111320.7020463578, 647795574.6671607, -4082003173.641316, 10774905663.51142, -15171875531.51559, 12053065338.62167, -5124939663.577472, 913311935.9512032, 67.5],
    [0.00337398766765, 111320.7020202162, 4481351.045890365, -23393751.19931662, 79682215.47186455, -115964993.2797253, 97236711.15602145, -43661946.33752821, 8477230.501135234, 52.5],
    [0.00220636496208, 111320.7020209128, 51751.86112841131, 3796837.749470245, 992013.7397791013, -1221952.21711287, 1340652.697009075, -620943.6990984312, 144416.9293806241, 37.5],
    [-0.0003441963504368392, 111320.7020576856, 278.2353980772752, 2485758.690035394, 6070.750963243378, 54821.18345352118, 9540.606633304236, -2710.55326746645, 1405.483844121726, 22.5],
    [-0.0003218135878613132, 111320.7020701615, 0.00369383431289, 823725.6402795718, 0.46104986909093, 2351.343141331292, 1.58060784298199, 8.77738589078284, 0.37238884252424, 7.45]
]

function getRange(cC, cB, T) {
    if (cB != null) {
        cC = Math.max(cC, cB);
    }
    if (T != null) {
        cC = Math.min(cC, T);
    }
    return cC;
}

function getLoop(cC, cB, T) {
    while (cC > T) {
        cC -= T - cB;
    }
    while (cC < cB) {
        cC += T - cB;
    }
    return cC;
}

function convertor(cC, cD) {
    if (!cC || !cD) {
        return null;
    }
    let T = cD[0] + cD[1] * Math.abs(cC.x);
    const cB = Math.abs(cC.y) / cD[9];
    let cE = cD[2] + cD[3] * cB + cD[4] * cB * cB +
        cD[5] * cB * cB * cB + cD[6] * cB * cB * cB * cB +
        cD[7] * cB * cB * cB * cB * cB +
        cD[8] * cB * cB * cB * cB * cB * cB;
    T *= (cC.x < 0 ? -1 : 1);
    cE *= (cC.y < 0 ? -1 : 1);
    return [T, cE];
}

function convertLL2MC(T) {
    let cD, cC, len;
    T.x = getLoop(T.x, -180, 180);
    T.y = getRange(T.y, -74, 74);
    const cB = T;
    for (cC = 0, len = LLBAND.length; cC < len; cC++) {
        if (cB.y >= LLBAND[cC]) {
            cD = LL2MC[cC];
            break;
        }
    }
    if (!cD) {
        for (cC = LLBAND.length - 1; cC >= 0; cC--) {
            if (cB.y <= -LLBAND[cC]) {
                cD = LL2MC[cC];
                break;
            }
        }
    }
    const cE = convertor(T, cD);
    return cE;
}

convertLL2MC({x: 116.403095, y: 30.702984}) // [12958074.255013367,3572218.8142307573]

二、墨卡托坐标转经纬度坐标

var MCBAND = [12890594.86, 8362377.87, 5591021, 3481989.83, 1678043.12, 0]
var MC2LL = [
    [1.410526172116255e-8, 0.00000898305509648872, -1.9939833816331, 200.9824383106796, -187.2403703815547, 91.6087516669843, -23.38765649603339, 2.57121317296198, -0.03801003308653, 17337981.2],
    [-7.435856389565537e-9, 0.000008983055097726239, -0.78625201886289, 96.32687599759846, -1.85204757529826, -59.36935905485877, 47.40033549296737, -16.50741931063887, 2.28786674699375, 10260144.86],
    [-3.030883460898826e-8, 0.00000898305509983578, 0.30071316287616, 59.74293618442277, 7.357984074871, -25.38371002664745, 13.45380521110908, -3.29883767235584, 0.32710905363475, 6856817.37],
    [-1.981981304930552e-8, 0.000008983055099779535, 0.03278182852591, 40.31678527705744, 0.65659298677277, -4.44255534477492, 0.85341911805263, 0.12923347998204, -0.04625736007561, 4482777.06],
    [3.09191371068437e-9, 0.000008983055096812155, 0.00006995724062, 23.10934304144901, -0.00023663490511, -0.6321817810242, -0.00663494467273, 0.03430082397953, -0.00466043876332, 2555164.4],
    [2.890871144776878e-9, 0.000008983055095805407, -3.068298e-8, 7.47137025468032, -0.00000353937994, -0.02145144861037, -0.00001234426596, 0.00010322952773, -0.00000323890364, 826088.5]
]

function convertor(cC, cD) {
    if (!cC || !cD) {
        return null;
    }
    let T = cD[0] + cD[1] * Math.abs(cC.x);
    const cB = Math.abs(cC.y) / cD[9];
    let cE = cD[2] + cD[3] * cB + cD[4] * cB * cB +
        cD[5] * cB * cB * cB + cD[6] * cB * cB * cB * cB +
        cD[7] * cB * cB * cB * cB * cB +
        cD[8] * cB * cB * cB * cB * cB * cB;
    T *= (cC.x < 0 ? -1 : 1);
    cE *= (cC.y < 0 ? -1 : 1);
    return [T, cE];
}

function convertMC2LL(cB) {
    const cC = {
        x: Math.abs(cB.x),
        y: Math.abs(cB.y)
    };
    let cE;
    for (let cD = 0, len = MCBAND.length; cD < len; cD++) {
        if (cC.y >= MCBAND[cD]) {
            cE = MC2LL[cD];
            break;
        }
    }
    const T = convertor(cB, cE);
    return T;
}

convertMC2LL({x: 12958074.255013367, y: 3572218.8142307573}) // [116.40309499999992,30.7029838655178]