Use variables in for...of object loop

Question

I have a for...of loop for objects.

for(const {site, dt, cat, ...vals} of obj[key]) {
   ...
}

code with the help of @user120242: Original code

let obj= {
  'Jan 01': [
             {dt: 'Jan 01', cat: 'abc', site: 'google', val1:10, val2:20, val3:30},
             {dt: 'Jan 01', cat: 'abc', site: 'bing', val1:23, val2:12, val3:14},
             {dt: 'Jan 01', cat: 'abc', site: 'jeeves', val1:67, val2:78, val3:12},
             {dt: 'Jan 01', cat: 'pqr', site: 'google', val1:10, val2:20, val3:30},
             {dt: 'Jan 01', cat: 'pqr', site: 'bing', val1:23, val2:12, val3:14},
             {dt: 'Jan 01', cat: 'pqr', site: 'jeeves', val1:67, val2:78, val3:12},
             {dt: 'Jan 01', cat: 'xyz', site: 'google', val1:10, val2:20, val3:30},
             {dt: 'Jan 01', cat: 'xyz', site: 'bing', val1:23, val2:12, val3:14},
             {dt: 'Jan 01', cat: 'xyz', site: 'jeeves', val1:67, val2:78, val3:12}
            ],
  'Feb 01': [
             {dt: 'Feb 01', cat: 'abc', site: 'google', val1:12, val2:11, val3:41},
             {dt: 'Feb 01', cat: 'abc', site: 'bing', val1:45, val2:67, val3:0},
             {dt: 'Feb 01', cat: 'abc', site: 'jeeves', val1:78, val2:34, val3:41},
             {dt: 'Feb 01', cat: 'pqr', site: 'google', val1:44, val2:88, val3:5},
             {dt: 'Feb 01', cat: 'pqr', site: 'bing', val1:56, val2:11, val3:99},
             {dt: 'Feb 01', cat: 'pqr', site: 'jeeves', val1:22, val2:34, val3:77},
             {dt: 'Feb 01', cat: 'xyz', site: 'google', val1:33, val2:99, val3:34},
             {dt: 'Feb 01', cat: 'xyz', site: 'bing', val1:77, val2:55, val3:14},
             {dt: 'Feb 01', cat: 'xyz', site: 'jeeves', val1:33, val2:23, val3:98}
            ],
  'Mar 01': [
             {dt: 'Mar 01', cat: 'abc', site: 'google', val1:11, val2:20, val3:6},
             {dt: 'Mar 01', cat: 'abc', site: 'bing', val1:22, val2:91, val3:89},
             {dt: 'Mar 01', cat: 'abc', site: 'jeeves', val1:33, val2:81, val3:12},
             {dt: 'Mar 01', cat: 'pqr', site: 'google', val1:44, val2:71, val3:33},
             {dt: 'Mar 01', cat: 'pqr', site: 'bing', val1:55, val2:61, val3:14},
             {dt: 'Mar 01', cat: 'pqr', site: 'jeeves', val1:66, val2:51, val3:43},
             {dt: 'Mar 01', cat: 'xyz', site: 'google', val1:77, val2:41, val3:98},
             {dt: 'Mar 01', cat: 'xyz', site: 'bing', val1:88, val2:31, val3:23},
             {dt: 'Mar 01', cat: 'xyz', site: 'jeeves', val1:99, val2:21, val3:4}
            ]
}

for(const key of Object.keys(obj)) {
  const catMap = new Map()
  for(const {site, dt, cat, ...vals} of obj[key]) {
    const row = catMap.get(dt+','+cat)||{dt, cat}
    Object.entries(vals).forEach(([k,v])=>row[k]=(row[k]||0)+v)
    catMap.set(dt+','+cat, row)
  }
  obj[key] = [...catMap.values()]
}

console.log(obj);

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Code with Vars:

let obj= {
  'Jan 01': [
             {dt: 'Jan 01', cat: 'abc', site: 'google', val1:10, val2:20, val3:30},
             {dt: 'Jan 01', cat: 'abc', site: 'bing', val1:23, val2:12, val3:14},
             {dt: 'Jan 01', cat: 'abc', site: 'jeeves', val1:67, val2:78, val3:12},
             {dt: 'Jan 01', cat: 'pqr', site: 'google', val1:10, val2:20, val3:30},
             {dt: 'Jan 01', cat: 'pqr', site: 'bing', val1:23, val2:12, val3:14},
             {dt: 'Jan 01', cat: 'pqr', site: 'jeeves', val1:67, val2:78, val3:12},
             {dt: 'Jan 01', cat: 'xyz', site: 'google', val1:10, val2:20, val3:30},
             {dt: 'Jan 01', cat: 'xyz', site: 'bing', val1:23, val2:12, val3:14},
             {dt: 'Jan 01', cat: 'xyz', site: 'jeeves', val1:67, val2:78, val3:12}
            ],
  'Feb 01': [
             {dt: 'Feb 01', cat: 'abc', site: 'google', val1:12, val2:11, val3:41},
             {dt: 'Feb 01', cat: 'abc', site: 'bing', val1:45, val2:67, val3:0},
             {dt: 'Feb 01', cat: 'abc', site: 'jeeves', val1:78, val2:34, val3:41},
             {dt: 'Feb 01', cat: 'pqr', site: 'google', val1:44, val2:88, val3:5},
             {dt: 'Feb 01', cat: 'pqr', site: 'bing', val1:56, val2:11, val3:99},
             {dt: 'Feb 01', cat: 'pqr', site: 'jeeves', val1:22, val2:34, val3:77},
             {dt: 'Feb 01', cat: 'xyz', site: 'google', val1:33, val2:99, val3:34},
             {dt: 'Feb 01', cat: 'xyz', site: 'bing', val1:77, val2:55, val3:14},
             {dt: 'Feb 01', cat: 'xyz', site: 'jeeves', val1:33, val2:23, val3:98}
            ],
  'Mar 01': [
             {dt: 'Mar 01', cat: 'abc', site: 'google', val1:11, val2:20, val3:6},
             {dt: 'Mar 01', cat: 'abc', site: 'bing', val1:22, val2:91, val3:89},
             {dt: 'Mar 01', cat: 'abc', site: 'jeeves', val1:33, val2:81, val3:12},
             {dt: 'Mar 01', cat: 'pqr', site: 'google', val1:44, val2:71, val3:33},
             {dt: 'Mar 01', cat: 'pqr', site: 'bing', val1:55, val2:61, val3:14},
             {dt: 'Mar 01', cat: 'pqr', site: 'jeeves', val1:66, val2:51, val3:43},
             {dt: 'Mar 01', cat: 'xyz', site: 'google', val1:77, val2:41, val3:98},
             {dt: 'Mar 01', cat: 'xyz', site: 'bing', val1:88, val2:31, val3:23},
             {dt: 'Mar 01', cat: 'xyz', site: 'jeeves', val1:99, val2:21, val3:4}
            ]
}

let site_val = 'site';
let dt_val = 'dt'
let cat_val = 'cat'

for(const key of Object.keys(obj)) {
  const catMap = new Map()
  for(const {site_val, dt_val, cat_val, ...vals} of obj[key]) {
    const row = catMap.get(dt_val+','+cat_val)||{dt_val, cat_val}
    Object.entries(vals).forEach(([k,v])=>row[k]=(row[k]||0)+v)
    catMap.set(dt_val+','+cat_val, row)
  }
  obj[key] = [...catMap.values()]
}

console.log(obj);

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I want to use variables instead of site, dt, cat to make it more dynamic. When I use variables, I am getting undefined. How do I use variables?

It's not clear what you mean. In the code above, site, dt, cat, etc are variables — Phil
– Phil, Commented Jun 24, 2020 at 2:59
do you mean: {site: newVarName}? Or are you saying you want to customize what keys to extract, like {[keyNameVar]: myVar}? — user120242
– user120242, Commented Jun 24, 2020 at 3:03
Perhaps you could show what you mean by "When I use variables, I am getting undefined" by editing your question to actually show that code — Phil
– Phil, Commented Jun 24, 2020 at 3:03
No, you haven't. You said "When I use variables, I am getting undefined" but you have not explained what that means nor have you shown that code — Phil
– Phil, Commented Jun 24, 2020 at 3:11

user120242 · Accepted Answer · 2020-06-24 03:22:26Z

Using computed property name syntax { [computedName+'str']: varName } :

let obj= {
  'Jan 01': [
             {dt: 'Jan 01', cat: 'abc', site: 'google', val1:10, val2:20, val3:30},
             {dt: 'Jan 01', cat: 'abc', site: 'bing', val1:23, val2:12, val3:14},
             {dt: 'Jan 01', cat: 'abc', site: 'jeeves', val1:67, val2:78, val3:12},
             {dt: 'Jan 01', cat: 'pqr', site: 'google', val1:10, val2:20, val3:30},
             {dt: 'Jan 01', cat: 'pqr', site: 'bing', val1:23, val2:12, val3:14},
             {dt: 'Jan 01', cat: 'pqr', site: 'jeeves', val1:67, val2:78, val3:12},
             {dt: 'Jan 01', cat: 'xyz', site: 'google', val1:10, val2:20, val3:30},
             {dt: 'Jan 01', cat: 'xyz', site: 'bing', val1:23, val2:12, val3:14},
             {dt: 'Jan 01', cat: 'xyz', site: 'jeeves', val1:67, val2:78, val3:12}
            ],
  'Feb 01': [
             {dt: 'Feb 01', cat: 'abc', site: 'google', val1:12, val2:11, val3:41},
             {dt: 'Feb 01', cat: 'abc', site: 'bing', val1:45, val2:67, val3:0},
             {dt: 'Feb 01', cat: 'abc', site: 'jeeves', val1:78, val2:34, val3:41},
             {dt: 'Feb 01', cat: 'pqr', site: 'google', val1:44, val2:88, val3:5},
             {dt: 'Feb 01', cat: 'pqr', site: 'bing', val1:56, val2:11, val3:99},
             {dt: 'Feb 01', cat: 'pqr', site: 'jeeves', val1:22, val2:34, val3:77},
             {dt: 'Feb 01', cat: 'xyz', site: 'google', val1:33, val2:99, val3:34},
             {dt: 'Feb 01', cat: 'xyz', site: 'bing', val1:77, val2:55, val3:14},
             {dt: 'Feb 01', cat: 'xyz', site: 'jeeves', val1:33, val2:23, val3:98}
            ],
  'Mar 01': [
             {dt: 'Mar 01', cat: 'abc', site: 'google', val1:11, val2:20, val3:6},
             {dt: 'Mar 01', cat: 'abc', site: 'bing', val1:22, val2:91, val3:89},
             {dt: 'Mar 01', cat: 'abc', site: 'jeeves', val1:33, val2:81, val3:12},
             {dt: 'Mar 01', cat: 'pqr', site: 'google', val1:44, val2:71, val3:33},
             {dt: 'Mar 01', cat: 'pqr', site: 'bing', val1:55, val2:61, val3:14},
             {dt: 'Mar 01', cat: 'pqr', site: 'jeeves', val1:66, val2:51, val3:43},
             {dt: 'Mar 01', cat: 'xyz', site: 'google', val1:77, val2:41, val3:98},
             {dt: 'Mar 01', cat: 'xyz', site: 'bing', val1:88, val2:31, val3:23},
             {dt: 'Mar 01', cat: 'xyz', site: 'jeeves', val1:99, val2:21, val3:4}
            ]
}

let site_key = 'site';
let dt_key = 'dt'
let cat_key = 'cat'

for(const key of Object.keys(obj)) {
  const catMap = new Map()
  for(const {
       [site_key]:site_val,
       [dt_key]:dt_val,
       [cat_key]:cat_val, ...vals} of obj[key]) {
    const row = catMap.get(dt_val+','+cat_val)||{dt_val, cat_val}
    Object.entries(vals).forEach(([k,v])=>row[k]=(row[k]||0)+v)
    catMap.set(dt_val+','+cat_val, row)
  }
  obj[key] = [...catMap.values()]
}

console.log(obj);

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