Flatten a javascript object to pass as querystring

I have a javascript object that I need to flatten into a string so that I can pass as querystring, how would I do that? i.e:

{ cost: 12345, insertBy: 'testUser' } would become cost=12345&insertBy=testUser

I can't use jQuery AJAX call for this call, I know we can use that and pass the object in as data but not in this case. Using jQuery to flatten to object would be okay though.

Thank you.

Answers:

Answer

You want jQuery.param:

var str = $.param({ cost: 12345, insertBy: 'testUser' });
// "cost=12345&insertBy=testUser"

Note that this is the function used internally by jQuery to serialize objects passed as the data argument.

Answer

Here's a non-jQuery version:

function toQueryString(obj) {
    var parts = [];
    for (var i in obj) {
        if (obj.hasOwnProperty(i)) {
            parts.push(encodeURIComponent(i) + "=" + encodeURIComponent(obj[i]));
        }
    }
    return parts.join("&");
}
Answer

My ES6 version (pure Javascript, no jQuery):

function toQueryString(paramsObject) {
  return Object
    .keys(paramsObject)
    .map(key => `${encodeURIComponent(key)}=${encodeURIComponent(paramsObject[key])}`)
    .join('&')
  ;
}
Answer

This is an old question, but at the top of Google searches, so I'm adding this for completeness.

If 1) you don't want to user jQuery, but 2) you want to covert a nested object to a query string, then (building off of Tim Down and Guy's answers), use this:

function toQueryString(obj, urlEncode) {
    //
    // Helper function that flattens an object, retaining key structer as a path array:
    //
    // Input: { prop1: 'x', prop2: { y: 1, z: 2 } }
    // Example output: [
    //     { path: [ 'prop1' ],      val: 'x' },
    //     { path: [ 'prop2', 'y' ], val: '1' },
    //     { path: [ 'prop2', 'z' ], val: '2' }
    // ]
    //
    function flattenObj(x, path) {
        var result = [];

        path = path || [];
        Object.keys(x).forEach(function (key) {
            if (!x.hasOwnProperty(key)) return;

            var newPath = path.slice();
            newPath.push(key);

            var vals = [];
            if (typeof x[key] == 'object') {
                vals = flattenObj(x[key], newPath);
            } else {
                vals.push({ path: newPath, val: x[key] });
            }
            vals.forEach(function (obj) {
                return result.push(obj);
            });
        });

        return result;
    } // flattenObj

    // start with  flattening `obj`
    var parts = flattenObj(obj); // [ { path: [ ...parts ], val: ... }, ... ]

    // convert to array notation:
    parts = parts.map(function (varInfo) {
        if (varInfo.path.length == 1) varInfo.path = varInfo.path[0];else {
            var first = varInfo.path[0];
            var rest = varInfo.path.slice(1);
            varInfo.path = first + '[' + rest.join('][') + ']';
        }
        return varInfo;
    }); // parts.map

    // join the parts to a query-string url-component
    var queryString = parts.map(function (varInfo) {
        return varInfo.path + '=' + varInfo.val;
    }).join('&');
    if (urlEncode) return encodeURIComponent(queryString);else return queryString;
}

Use like:

console.log(toQueryString({
    prop1: 'x',
    prop2: {
        y: 1,
        z: 2
    }
}, false));

Which outputs:

prop1=x&prop2[y]=1&prop2[z]=2
Answer

Here is another non-jQuery version that utilizes lodash or underscore if you're already using one of those libraries:

var toQueryString = function(obj) {
  return _.map(obj,function(v,k){
    return encodeURIComponent(k) + '=' + encodeURIComponent(v);
  }).join('&');
};

^ I wrote that 5 years ago. An updated and more succinct version of this would now (Oct 2019) be:

var input = { cost: 12345, insertBy: 'testUser' };
Object.entries(input)
  .map(([k,v]) => `${encodeURIComponent(k)}=${encodeURIComponent(v)}`)
  .join('&');
// cost=12345&insertBy=testUser

Check that the runtime that you're targeting supports Object.entries() or that you're using a transpiler like Babel or TypeScript if it doesn't.

Answer

Try the $.param() method:

var result = $.param({ cost: 12345, insertBy: 'testUser' });
Answer

General JavaScript:

function toParam(obj) {
  var str = "";
  var seperator = "";
  for (key in obj) {
    str += seperator;
    str += enncodeURIComponent(key) + "=" + encodeURIComponent(obj[key]);
    seperator = "&";
  }
  return str;
}


toParam({ cost: 12345, insertBy: 'testUser' })
"cost=12345&insertBy=testUser"
Answer

Another version:

function toQueryString(obj) {
    return Object.keys(obj).map(k => {
      return encodeURIComponent(k) + "=" + encodeURIComponent(obj[k])
    })
    .join("&");
}
Answer
var myObj = { cost: 12345, insertBy: 'testUser' },
    param = '',
    url   = 'http://mysite.com/mypage.php';    

for (var p in myObj) {
  if (myObj.hasOwnProperty(p)) {
    param += encodeURIComponent(p) + "=" + encodeURIComponent(myObj[p]) + "&";
  }
}

window.location.href = url + "?" + param;
Answer

you can use this

function serialize(obj)
{
    let str = []

    for(var p in obj)
    {
      if(obj.hasOwnProperty(p)) str.push(encodeURIComponent(p) + '=' + encodeURIComponent(obj[p]))
    }

    return str.join('&')
}

try on JSFiddle on this link https://jsfiddle.net/yussan/kwmnkca6/

Answer

ES6 version of Jrop's answer (also parses nested params)

const toQueryString = (obj, urlEncode = false) => {
  if (!obj) return null;
  const flattenObj = (x, path = []) => {
    const result = [];
    Object.keys(x).forEach((key) => {
      if (!Object.prototype.hasOwnProperty.call(x, key)) return;
      const newPath = path.slice();
      newPath.push(key);
      let vals = [];
      if (typeof x[key] === 'object') {
        vals = flattenObj(x[key], newPath);
      } else {
        vals.push({ path: newPath, val: x[key] });
      }
      vals.forEach((v) => {
        return result.push(v);
      });
    });
    return result;
  };

  let parts = flattenObj(obj);
  parts = parts.map((varInfo) => {
    if (varInfo.path.length === 1) {
      varInfo.path = varInfo.path[0]; // eslint-disable-line no-param-reassign
    } else {
      const first = varInfo.path[0];
      const rest = varInfo.path.slice(1);
      varInfo.path = `${first}[${rest.join('][')}]`; // eslint-disable-line no-param-reassign
    }
    return varInfo;
  });

  const queryString = parts.map((varInfo) => {
    return `${varInfo.path}=${varInfo.val}`;
  }).join('&');
  if (urlEncode) {
    return encodeURIComponent(queryString);
  }
  return queryString;
};

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