如有必要，获取带有姓氏缩写的名字列表

Question

So in my JS I have an object like so;

[
    {
        firstname: "John",
        lastname: "Smith"
    },
    {
        firstname: "Peter",
        lastname: "Gregory"
    },
    {
        firstname: "John",
        lastname: "Fisher"
    },
    {
        firstname: "Sam",
        lastname: "Fisher"
    }
]

And I'd like to display the first names in a comma-separated string. Now this would be simple enough, but I also want to display the first initial of the last name only where necessary, to distinguish two people with the same first name.

So, in the end, I'd have this:

John S., Peter, John F., Sam

Thus far I've been able to do a loop that remembers past initials, but the problem for me becomes the fourth entry in the example; someone with a last name that has had to be distinguished with someone else, but who doesn't a share a first name with anyone.

What would be the smartest way of going about this?

Answer 1

Array.map + Array.join will do it. I included a polyfill for Array.map if you need it at the bottom.

 var people = [ { firstname: "John", lastname: "Smith" }, { firstname: "Peter", lastname: "Gregory" }, { firstname: "John", lastname: "Fisher" }, { firstname: "Sam", lastname: "Fisher" } ] /* Count number of firstNames */ var firstnames = {}; for (var i = 0; i < people.length; i++) { if (!firstnames[people[i].firstname]) { firstnames[people[i].firstname] = 0; } firstnames[people[i].firstname] ++; } /* Create the string of names */ var peopleString = people.map(function (a) { /* Check if we need a last name here */ var lastname = firstnames[a.firstname] > 1 ? (a.lastname ? ' ' + a.lastname.substr(0, 1) + '.' : '') : ''; return a.firstname + lastname; }).join(', '); document.write(peopleString); /*Polyfill for Array.map taken from MDN: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/map#Polyfill*/ // Production steps of ECMA-262, Edition 5, 15.4.4.19 // Reference: http://es5.github.io/#x15.4.4.19 if (!Array.prototype.map) { Array.prototype.map = function(callback, thisArg) { var T, A, k; if (this == null) { throw new TypeError(' this is null or not defined'); } // 1. Let O be the result of calling ToObject passing the |this| // value as the argument. var O = Object(this); // 2. Let lenValue be the result of calling the Get internal // method of O with the argument "length". // 3. Let len be ToUint32(lenValue). var len = O.length >>> 0; // 4. If IsCallable(callback) is false, throw a TypeError exception. // See: http://es5.github.com/#x9.11 if (typeof callback !== 'function') { throw new TypeError(callback + ' is not a function'); } // 5. If thisArg was supplied, let T be thisArg; else let T be undefined. if (arguments.length > 1) { T = thisArg; } // 6. Let A be a new array created as if by the expression new Array(len) // where Array is the standard built-in constructor with that name and // len is the value of len. A = new Array(len); // 7. Let k be 0 k = 0; // 8. Repeat, while k < len while (k < len) { var kValue, mappedValue; // a. Let Pk be ToString(k). // This is implicit for LHS operands of the in operator // b. Let kPresent be the result of calling the HasProperty internal // method of O with argument Pk. // This step can be combined with c // c. If kPresent is true, then if (k in O) { // i. Let kValue be the result of calling the Get internal // method of O with argument Pk. kValue = O[k]; // ii. Let mappedValue be the result of calling the Call internal // method of callback with T as the this value and argument // list containing kValue, k, and O. mappedValue = callback.call(T, kValue, k, O); // iii. Call the DefineOwnProperty internal method of A with arguments // Pk, Property Descriptor // { Value: mappedValue, // Writable: true, // Enumerable: true, // Configurable: true }, // and false. // In browsers that support Object.defineProperty, use the following: // Object.defineProperty(A, k, { // value: mappedValue, // writable: true, // enumerable: true, // configurable: true // }); // For best browser support, use the following: A[k] = mappedValue; } // d. Increase k by 1. k++; } // 9. return A return A; }; } 

Answer 2

I guess you could do something like this:

var o = {};
var arr = [];
people.forEach(function(val) {
    if (!o.hasOwnProperty(val.firstname)) {
       // didn't see this name before,
       // keeping it so we know we saw it
       // and keeping its index, in case we see the same name again
       var idx = arr.push(val.firstname);
        o[val.firstname] = { idx: idx - 1, val: val };

    }
    else {
        // we saw this name, adding the current with a last name
        // also adding last name to the origninal we saved before
        arr.push(val.firstname + " " + val.lastname.substr(0, 1));
        arr[o[val.firstname].idx] = o[val.firstname].val.firstname + " " + o[val.firstname].val.lastname.substr(0, 1);
    }
})
console.log(arr);

Answer 3

Just if you want an (almost) inline solution...

var arr = [
    {
        firstname: "John",
        lastname: "Smith"
    },
    {
        firstname: "Peter",
        lastname: "Gregory"
    },
    {
        firstname: "John",
        lastname: "Fisher"
    },
    {
        firstname: "Sam",
        lastname: "Fisher"
    }
];

var out = arr.map (function(i){
    return arr.filter(function(e){
        return e.firstname == i.firstname && true;
    }, []).length > 1 ? (i.firstname + " " + i.lastname.charAt(0)) : (i.firstname);
}, []).toString();

console.log(out);

fiddle http://jsfiddle.net/owqc35p3/2/

It will not be that performant compared to many others though, because we're looping arr every time inside the current arr map (also, .toString() can be replaced by .join(" ,"); )