How to convert a plain object into an ES6 Map

Question

For some reason I can t find this simple thing in the MDN docs  maybe I m just missing it    I expected this to work   const map   new Map  foo   bar      map get  foo        bar       but the first line throws TypeError   var  Symbol iterator  is not a function  How do I make a Map from a plain object  Do I really have to first convert it into an array of arrays of key-value pairs

User · Answer

The answer by Nils describes how to convert objects to maps  which I found very useful  However  the OP was also wondering where this information is in the MDN docs  While it may not have been there when the question was originally asked  it is now on the MDN page for Object entries   under the heading Converting an Object to a Map which states      Converting an Object to a Map      The new Map   constructor accepts an iterable of entries  With Object entries  you can easily convert from Object to Map   const obj     foo   bar   baz  42     const map   new Map Object entries obj    console log map      Map   foo   bar   baz  42

User · Answer

Yes  the Map constructor takes an array of key-value pairs   Object entries is a new Object static method available in ES2017  19 1 2 5    const map   new Map Object entries  foo   bar       map get  foo        bar    It s currently implemented in Firefox 46  and Edge 14  and newer versions of Chrome  If you need to support older environments and transpilation is not an option for you  use a polyfill  such as the one recommended by georg   Object entries   typeof Object entries      function    Object entries   obj   gt  Object keys obj  map k   gt   k  obj k

User · Answer

ES6  convert object to map   const objToMap    o    gt  new Map Object entries o      convert map to object   const mapToObj    m    gt      m  reduce   o v   gt   o v 0     v 1   return o           Note  the mapToObj function assumes map keys are strings  will fail otherwise

User · Answer

const myMap   new Map      Object          keys myObj           map              key   gt   key  myObj key

User · Answer

Do I really have to first convert it into an array of arrays of key-value pairs    No  an iterator of key-value pair arrays is enough  You can use the following to avoid creating the intermediate array   function  entries obj        for  let key in obj          yield  key  obj key       const map   new Map entries  foo   bar      map get  foo        bar

User · Answer

Alternatively you can use the lodash toPairs method   const     require  lodash    const map   new Map   toPairs  foo   bar

[javascript] How to convert a plain object into an ES6 Map?

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