Remove a key:value from an JSON object using jq

Question

I’m trying to add and remove a 'key:value' from a JSON object using jq. I’m new using jq and I do not understand the errors that jq is throwing at me, so any help pushing me in the correct direction is greatly appreciated. My specific issue is I have a JSON object (below) and I want to be able to add/remove the “maxHeight” key/value from the JSON object.

Some commands I’ve tried with the errors I get…

jq 'recurse(.[]) |= del(.maxHeight)' new.json   

Cannot iterate over null (null)

 jq 'recurse(.[]) |= {maxHeight}' new.json

Cannot iterate over string ("feature")

jq 'recurse(.[]) |= .maxHeight' new.json 

Cannot index string with string "style"

new.json file looks like this...

{
  "style": {
    "className": "feature",
    "showLabels": false,
    "color": "function(feature, variableName, glyphObject, track){if(feature.get(\"type\") === \"CDS\"){return \"#9CFBF5\";} else if(feature.get(\"type\") === \"exon\"){return \"#43A47F\";} else if(feature.get(\"type\") === \"intron\"){return \"#E8E8E8\";} else if(feature.get(\"type\") === \"five_prime_UTR\"){return \"#F192FE\";} else if(feature.get(\"type\") === \"three_prime_UTR\"){return \"#FEC892\";} else {return \"#FF0000\";}}",
    "arrowheadClass": null,
    "featureCss": "padding:3px;"
  },
  "menuTemplate": [
    {
      "label": "View details"
    },
    {
      "label": "Highlight a gene"
    },
    {
      "iconClass": "dijitIconBookmark",
      "content": "function(track,feature,div) { window.parent.angular.element(window.frameElement).scope().specificNote( feature[2] ) }",
      "action": "contentDialog",
      "title": "(feature{name})",
      "label": "Create Note"
    }
  ],
  "hooks": {
    "modify": " function(track,feature,div){   var checkArr=[\"Reference\",\"Missing\",\"Heterozygous\",\"NonReference\"];for(var i=0;i<feature.length;i++){for(var j=0;j<checkArr.length;j++){  if( i>3) { if( feature[i] ===  checkArr[j] ) {  if(feature[i]==\"NonReference\"){div.style.backgroundColor=\"red\"}else if(feature[i]==\"Reference\"){div.style.backgroundColor=\"green\"}else if(feature[i]==\"Heterozygous\"){div.style.backgroundColor=\"orange\"}else if(feature[i]==\"Missing\"){div.style.backgroundColor=\"grey\"} }}}}} "
  },
  "key": "cucumber_ChineseLong_v2.gff3",
  "storeClass": "JBrowse/Store/SeqFeature/NCList",
  "trackType": null,
  "maxHeight": "200px",
  "urlTemplate": "tracks/cucumber_ChineseLong_v2.gff3/{refseq}/trackData.json",
  "compress": 0,
  "label": "cucumber_ChineseLong_v2.gff3",
  "type": "JBrowse/View/Track/CanvasFeatures"
}

Answer 1

Using jq-1.6, this deletes the key .maxHeight from the input (it doesn't even complain if it didn't exist before):

jq 'del(.maxHeight)' new.json

Answer 2

For very large JSON documents, it may be preferable to use jq's "streaming parser" for this kind of problem, at least if the editing operations greatly reduce the size of the document. At any rate, here is a solution that uses the --stream option:

jq --stream 'select(length == 2 and .[0][-1] == "maxHeight" | not)' new.json |
 jq -n 'fromstream(inputs)'

Note that the -n option must be used in the second call to jq.