JSFiddle - React, Tailwind, and code Playground

HTML

<table>    
    <tr>
        <td>
          <select style="width:5em;" class="field">
            <option></option>
            <option>name</option>
            <option>age</option>
            <option>sex</option>
          </select>
        </td> 
        <td>
          <select style="width:5em;" class = "comp">
            <option></option>
            <option>equals</option>
            <option>starts with</option>
            <option>not equal to</option>
          </select>
        </td>
        <td><input type="text" class = 'value'></td>
   </tr>
   <tr>
        <td>
          <select style="width:5em;" class="field">
            <option></option>
            <option>name</option>
            <option>age</option>
            <option>sex</option>
          </select>
        </td> 
        <td>
          <select style="width:5em;" class = "comp">
            <option></option>
            <option>equals</option>
            <option>starts with</option>
            <option>not equal to</option>
          </select>
        </td>
        <td><input type="text" class = 'value'></td>
   </tr>  
   <tr>
        <td>
          <select style="width:5em;" class="field">
            <option></option>
            <option>name</option>
            <option>age</option>
            <option>sex</option>
          </select>
        </td> 
        <td>
          <select style="width:5em;" class = "comp">
            <option></option>
            <option>equals</option>
            <option>starts with</option>
            <option>not equal to</option>
          </select>
        </td>
        <td><input type="text" class = 'value'></td>
   </tr>           
    
</table>
<input type="button" value = "go" id="out">

JavaScript

// object to hold your data
function dataRow(value1,value2,value3) {
    this.name = value1;
    this.comparison = value2;
    this.value = value3;
}

$('#out').click(function(){   
    
    // create array to hold your data
    var dataArray = new Array();
    
    // iterate through rows of table
    for(var i = 1; i <= $("table tr").length; i++){
        
        // check if first field is used
        if($("table tr:nth-child(" + i + ") select[class='field']").val().length > 0) {
            
            // create object and push to array
            dataArray.push(    
                new dataRow(
                    $("table tr:nth-child(" + i + ") select[class='field']").val(),
                    $("table tr:nth-child(" + i + ") select[class='comp']").val(),
                    $("table tr:nth-child(" + i + ") input").val())
            );
        }
        
    }
    
    // consider using a JSON library to do this for you
    for(var i = 0; i < dataArray.length; i++){
        var output = "";
        output = output + '{"name":"data' + (i + 1) + '.' + dataArray[i].name + '",';
        output = output + '"comparison":"data' + (i + 1) + '.' + dataArray[i].comparison + '",';
        output = output + '"value":"data' + (i + 1) + '.' + dataArray[i].value + '"}';
        alert(output);
    }
})