Javascript How to update value in array based on matching value in different array

Question

I am trying to figure out a way to take a string and update values based on a new string that is coming in. The string represents the structure of a table and contains a column name and a column data type.

To do this I am trying to convert the original string and the new string into arrays. Then I need to union the results but update existing columns with their new data types.

For instance, in the below example I want to return 4 columns where col2 is updated from varchar(30 to varchar(20).

var original_schema = 'col1 int,col2 varchar(30),col3 datetime2,col5 bit';
var new_schema = 'col1 int,col2 varchar(20),col3 datetime2,col4 int';

var arr_original_schema = original_schema.replace(/ /g,':').split(",");
var arr_new_schema = new_schema.replace(/ /g,':').split(",");

console.log(arr_original_schema);
console.log(arr_new_schema);

function arrayUnique(array) {
    var a = array.concat();
    for(var i=0; i<a.length; ++i) {
        for(var j=i+1; j<a.length; ++j) {           
            //removed
          if(a[i] === a[j])            
                a.splice(j--, 1);
        }
    }

    return a;
}

var uniqueschema = arrayUnique(arr_original_schema.concat(arr_new_schema));
console.log(uniqueschema)

The expected result is: col1 int,col2 varchar(20),col3 datetime2,col4 int,col5 bit"

Please add example of final expected result

MonteCristo
– MonteCristo

2020-03-19 20:42:49 +00:00
Commented Mar 19, 2020 at 20:42 — MonteCristo
– MonteCristo, Commented Mar 19, 2020 at 20:42
Thank you, I added my expected results.

CodeMonkey
– CodeMonkey

2020-03-19 21:19:19 +00:00
Commented Mar 19, 2020 at 21:19 — CodeMonkey
– CodeMonkey, Commented Mar 19, 2020 at 21:19

baao · Accepted Answer · 2020-03-19 21:49:19Z

1

I'd create objects of it, then use Object.assign

const original_schema = 'col1 int,col2 varchar(30),col3 datetime2,col5 bit';
const new_schema = 'col1 int,col2 varchar(20),col3 datetime2,col4 int';

const objectify = (string) => string.split(',').reduce((a, b) => {
    const [col, type] = b.split(/\s+/);
    a[col] = type;
    return a;
}, {});

const os = objectify(original_schema);
const ns = objectify(new_schema);

const res = Object.entries(Object.assign(os, ns)).map(e => e.join(' ')).join(',');
console.log(res);

answered Mar 19, 2020 at 21:49

baao

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Comments

koalaok · Accepted Answer · 2020-03-19 21:25:21Z

1

var original_schema = 'col1 int,col2 varchar(30),col3 datetime2';
var new_schema = 'col1 int,col2 varchar(20),col3 datetime2,col4 int';


const arr_1 = original_schema.split(',');
const arr_0 = (new Array(arr_1.length)).fill(null);
let arr_2 = new_schema.split(',')
arr_2=Object.assign(arr_0, arr_2)

const result =  arr_2.filter(function (el) {
  return el != null;
}).join(',')

console.log(result);

edited Mar 19, 2020 at 21:25

answered Mar 19, 2020 at 20:42

koalaok

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8 Comments

ggorlen Over a year ago

This fails to union the schemas correctly; properties from a that aren't in b aren't carried through.

koalaok Over a year ago

"For instance, in the below example I want to return 4 columns where col2 is updated from varchar(30 to varchar(20)." he doesn't want union he wants overriding...

ggorlen Over a year ago

I'm talking about properties that aren't in b. In the example, there's an extra column in b, but switch the two around so there's an extra column in a that doesn't exist in b. For example, "a int, b int" and "a float" we should get "a float, b int".

koalaok Over a year ago

my snippet result is "col1 int,col2 varchar(20),col3 datetime2,col4 int" which is the expected result from the question. isn't it?

ggorlen Over a year ago

Yes, it works on that input but fails on the above case.

|

MonteCristo · Accepted Answer · 2020-03-19 21:53:25Z

const original_schema = 'col1 int,col2 varchar(30),col3 datetime2,col5 bit';
const new_schema = 'col1 int,col2 varchar(20),col3 datetime2,col4 int';

const originalArr = original_schema.split(",");
const newArr = new_schema.split(",");

// Create single array with duplicates
const mergedArray = [...originalArr, ...newArr];

// Run through merged array with duplicates and create/overwrite existing values
let mergedObj = mergedArray.reduce((acc, item) => {
  let [id, str] = item.split(' ');
  acc[id] = item;
  return acc;
}, {});

// sort the values of object using local compare
// Assume that each value always start with col and number and they should be ordered as such.
// use localCompare to compre these values.
let sorted = Object.values(mergedObj).sort((a, b) => a.localeCompare(b));

console.log(sorted.join(','));

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