This function will convert the Well Known Text to JSON for ESRI Geometry creation. See example at http://jsfiddle.net/mac1175/6hcax/

Convert WKT to Json for ESRI JSAPI

// from https://gist.github.com/mitch-cohen/9547514
export function toJson(WKTstr: string) {

    // trim leading "(" and trailing ")" characters
    function unbracket(str: string) {
        let left = str.indexOf("(") + 1;
        let right = str.lastIndexOf(")");
        if (right < str.length - 1) right = str.length;
        return str.substring(left, right);
    }

    function convertToPoint(pt: string) {
        return pt.trim().split(" ").map(parseFloat);
    };

    function convertToPointArray(ptArrayString: string) {
        return ptArrayString.split(",").map(convertToPoint);
    };

    let mods = {
        POINT: function (tailStr: string) {
            var point = convertToPoint(unbracket(tailStr));
            return {
                type: 'point',
                x: point[0],
                y: point[1],
            };
        },

        MULTIPOINT: function (tailStr: string) {
            let points = unbracket(tailStr).split("),").map(v => unbracket(v));
            return {
                type: 'multipoint',
                points: points.map(convertToPoint)
            };
        },

        LINESTRING: function (tailStr: string) {
            return {
                type: 'linestring',
                points: convertToPointArray(unbracket(tailStr))
            };
        },

        MULTILINESTRING: function (tailStr: string) {
            let pathsRaw = unbracket(tailStr).split("),").map(v => unbracket(v));
            let paths = pathsRaw.map(convertToPointArray);
            return {
                type: 'multilinestring',
                paths: paths
            };
        },

        POLYGON: function (tailStr: string) {
            return {
                type: 'polygon',
                rings: mods.MULTILINESTRING(tailStr).paths
            };
        },

        MULTIPOLYGON: function (tailStr: string) {
            tailStr = unbracket(tailStr);
            let pathsRaw = tailStr.split("),").map(v => unbracket(v));
            return {
                type: 'multipolygon',
                rings: pathsRaw.map(rings => mods.MULTILINESTRING(rings).paths)
            };
        },

    };

    let firstParenIndex = WKTstr.indexOf("(");
    let head = WKTstr.substring(0, firstParenIndex).trim() as keyof typeof mods;
    let tail = WKTstr.substr(firstParenIndex).trim();

    let mod = mods[head];

    return mod(tail) as {
        type: "point";
        x: number;
        y: number;
    } | {
            type: "polyline";
            paths: number[][][];
        } | {
            type: "multipoint";
            points: number[][];
        } | {
            type: "polygon";
            rings: number[][][];
        };
}