ChainContainer

Value this container stores, can be anythhing.

Also access through ChainContainer#close

Creates a new chain container holding the value returned from functor(this.value)

value = 2;
plus2 = (value) => value + 2;

chain(value)
 .chain(plus2) // 2 + 2
 .chain(plus2) // 4 + 2
 .debug()
 .chain(plu2)  // 6 + 2
 .close();

// 6
// 8

Or even combine with other utility methods

badStr = 'I%20am%20the%20very%20model%20of%20a%20modern%20Major'
 + '-General%0AI\'ve%20information%20vegetable%2C%20animal%2C%20'
 + 'and%20mineral%0AI%20know%20the%20kings%20of%20England%2C%20'
 + 'and%20I%20quote%20the%20fights%0AHistorical%0AFrom%20Marath'
 + 'on%20to%20Waterloo%2C%20in%20order%20categorical';

chain(badStr)
    .chain(decodeURIComponent)
    .chain(v => v.split('\n'))
    // .debug()                  // check the values along the way
    .chainMap(line => ({ line, length: line.length }))
    .chain(values => utils.table(values).render());

and it renders out a lovely table like this:

Assuming that value is an array, this maps fn to filter the results in the array.

chain([1,2,3,4])
   .chainFilter((value) => value < 3)
   .close();
// [1, 2]

Assuming that value is an array, performs a javaScript flatMap against the results.

This can be very helpful in expanding the list of items in an array, or removing items from an array.

// expanding size of the array
initializeArray = (size) => Array.from(Array(size)).map((val, index) => index);
initializeArray(3); // [0, 1, 2]

utils.chain([1, 2, 3, 4])
 .chainFlatMap(initializeArray)
 .close();

// [1, 1, 2, 1, 2, 3, 1, 2, 3, 4];

or similar to chainFilter

// reducing the size of the array
filterOdd = (value) => value % 2 === 0 ? [value] : [];
filterOdd(2); // [2]
filterOdd(1); // []

chain([1, 2, 3, 4, 5])
 .chainFlatMap(filterOdd)
 .close();

// [2, 4];

Assuming that value is an array, performs a javaScript forEach against the results.

This will run the passed function against every element in the result, without replacing the element with the returned value and makes inline editing simpler.

list = [{ first: 'john', last: 'doe' }, { first: 'jane', last: 'doe' }];
utils.chain(list)
 .mapForEach((entry) => entry.name = `${entry.first} ${entry.last})
 .close();
// [{ first: 'john', last: 'doe', name: 'john doe' }, { first: 'jane', last: 'doe', name: 'jane doe' }]

This is in contrast to chainMap, that replaces the element with the value returned.

Assuming that value is an array, this does a javascript array.map and applies fn to every value in the array.

initializeArray = (size) => Array.from(Array(size)).map((val, index) => index);
initializeArray(3); // [0, 1, 2]

addTwo = (value) => value + 2;
addTwo(3); // 5

utils.chain(3)
  .chain(initializeArray) // [0, 1, 2]
  .chainMap(addTwo) // [2, 3, 4] or [0 + 2, 1 + 2, 2 + 2]
  .chainMap(addTwo)
  .close();

// [4, 5, 6]

This is in contrast to chainForEach

Assuming that the value is an array, performs a reduce using fn and initialValue

initializeArray = (size) => Array.from(Array(size)).map((val, index) => index);
initializeArray(3); // [0, 1, 2]

addTwo = (value) => value + 2;
addTwo(3); // 5

utils.chain(3)
  .chain(initializeArray) // [0, 1, 2]
  .chainMap(addTwo) // [2, 3, 4] or [0 + 2, 1 + 2, 2 + 2]
  .debug()
  .chainReduce((result, value) => result + value, 0)
  .close();

// [2, 3, 4]
// 9

Clones the value, and ties the output to this cell.

Closes the chain and returns the current value.

Console.logs the value, and returns the unmodified current value.

value = 2;
plus2 = (value) => value + 2;

chain(value)
 .chain(plus2) // 2 + 2
 .chain(plus2) // 4 + 2
 .debug()
 .chain(plu2)  // 6 + 2
 .debug((value) => console.log(value))
 .close();

// 6
// 8
// 8

Function to call if an error occurs anywhere on the chain.

someErrorOccurred = false;
flipSwitch = (err) => {
  console.log('custom handler');
  someErrorOccurred = true;
};
throwError = () => {
  throw Error('Custom Error');
};

chain(2)
  .errorHandler(flipSwitch)
  .chain((value) => value + 2)
  .chain(throwError);

// customHandler
// {
//   "name": "Error",
//   "message": "Custom Error"
// }
// /Users/proth/Documents/notebooks/jupyter-ijavascript-utils/src/chain.js:175
//     throw err;
//     ^
// 
// Error: Custom Error
//     at throwError (evalmachine.<anonymous>:7:9)

Applies a function against the current value, while not passing the results along the chain.

results = [{ userId: 'abc123' }, { userId: 'xyz987' }];

activeUsers = chain(results)
 .chainMap((record) => users.get(record.userId))
 .chainForEach(record => record.status =  'active')
 .chain(records => d3.csv.format(records))
 .execute(records => utils.file.writeFile('./log', d3.csv.format(records)))
 .close()

Normally, you will want to replace the value in the chain based on the current value.

This replaces the value regardless, and is rarely used.