How to convert an Array to a JSON Obejct and vice versa

To dump a RMP array (json of arrays) to a google spreadsheet, you have to create an array of jsons: you'll have to use ${transpose(my_array)}.

To dump the rows of a google spreadsheet (array of jsons) to a RMP array (json of arrays), you have to use ${transpose_1(my_array)} defined below.

Code:

<#function transpose_1 my_array my_keys=[]>  
    ${my_array?size}  
    <#if my_array?is_sequence>  
        <#if (my_array?size > 0)>  
            <#if (my_keys?size != 0)>  
                <#assign array_keys = my_keys>  
            <#else>  
                <#assign array_keys = []>  
                <#list my_array[0]?keys as x>  
                    <#assign array_keys = array_keys + [x]>  
                </#list>  
            </#if>  
        </#if>  
        <#assign my_result = {}>

        <#list array_keys as x>  
            <#assign my_col = []>  
            <#list my_array as y>  
                <#assign my_col = my_col + [y[x]?default("")]>  
            </#list>  
            <#assign my_json = "{\"" + x + "\":" + my_col + "}">  
            <#assign my_json = my_json?eval>  
            <#assign my_result = (my_result + my_json)?eval>  
        </#list>  
    <#else>  
        <#assign my_result = "error while executing function tranpose_1">  
    </#if>
    <#return my_result>  
</#function>

Result:

<#assign my_array = {"col1": ["a","b"], "col2": ["c","d"], "col3": ["e","f"]}>
${my_array}  
<!-- json of arrays 
{
    "col1": ["a","b"],
    "col2":["c","d"],
    "col3":["e","f"]
} 
-->

<#assign my_array1 = transpose(my_array)>  
${my_array1}  
<!-- array of jsons 
[
    {
        "col1": "a",
        "col2": "c",
        "col3": "e"
    },
    {
        "col1": "b",
        "col2": "d",
        "col3": "f"
    }
]
-->

${transpose_1(my_array1)}  
<!-- 
{
    "col1": ["a", "b"],
    "col2": ["c", "d"],
    "col3": ["e", "f"]
}
-->

<!-- to retrieve only columns col1 and col2 (not col3)-->
${transpose_1(my_array1,["col1", "col2"])} 
<!-- 
{
    "col1": ["a", "b"],
    "col2": [ "c", "d"]
}
-->