<s>[INST] How do you write the Viterbi algorithm in JavaScript? [/INST] Here is the Viterbi algorithm in Javascript:

```js
function Viterbi(data) {
    var V = [{}];
    var path = {};
 
    // Initialize base cases (t == 0)
    for(var i=0;i<data.states.length;i++) {
        var state = data.states[i];
        V[0][state] = data.start_probability[state] * data.emission_probability[state][data.observations[0]];
        path[state] = [state];
    }

    // Run Viterbi for t > 0
    for(var t=1;t<data.observations.length;t++) {
        V.push({});
        var newpath = {};
        
        for(var i=0;i<data.states.length;i++) {
            var state = data.states[i];
            var max = [0,null];
            for(var j=0;j<data.states.length;j++) {
                var state0 = data.states[j];
                // Calculate the probablity
                var calc = V[t-1][state0]
                    * data.transition_probability[state0][state]
                    * data.emission_probability[state][data.observations[t]];
                if(calc > max[0]) max = [calc,state0];
            }
            V[t][state] = max[0];
            newpath[state] = path[max[1]].concat(state);
        }
        path = newpath;
    }

    var max = [0,null];
    for(var i=0;i<data.states.length;i++) {
        var state = data.states[i];
        var calc = V[data.observations.length-1][state];
        if(calc > max[0]) max = [calc,state];
    }
 
    return [max[0], path[max[1]]];
}
```</s>\ <s>[INST] can you give me an example usage? [/INST] Given a sequence of observed events, the Viterbi algorithm can be used to obtain a maximum (posterior) probability estimate of the most likely sequence of hidden states. This sequence of hidden states is called the Viterbi path.

An example usage is speech-to-text. The observed sequence of events is the acoustic signal of the speech, and the string of text to output is modeled as the most likely sequence of hidden states.</s>