Automat

function Automat (inpstr) {
    this.finstate=inpstr.length;
    let alphabet = new Array();
    let del = new Array();

    for (let j = 0; j <= inpstr.length; j++) {
        del[j] = new Array();
    }
    for (let i = 0; i < inpstr.length; i++) {
        alphabet[inpstr.charAt(i)] = 0;
    }
    for (let i in alphabet) {
        del[0][i] = 0;
    }
    for (let j = 0; j < inpstr.length; j++) {
        let prev = del[j][inpstr.charAt(j)];
        del[j][inpstr.charAt(j)] = j + 1;
        for(let i in alphabet) {
            del[j + 1][i] = del[prev][i];
        }
    }

    this.state = 0;
    this.change = function (symbol) {
        if (del[this.state][symbol] == null) {
            this.state = 0;
        } else {
            this.state = del[this.state][symbol];
            return this.finstate == this.state;
        }
    }
}


function Find(text, target) {
    let result = [];
    var automat = new Automat(target);

    for (let i = 0; i < text.length; i++) {
        if (automat.change(text.charAt(i))) {
            result.push(i - target.length + 1);
        }
    }

    if (result.length == 0) console.log('Not found!');
    return result;
}


test();
function test() {
    const fs = require('fs');
    let text = fs.readFileSync("message.txt", "utf8");
    let target = "ef"
    let indexes = Find(text, target);
    console.log(indexes);
}