JS在对象数组上使用indexOf

Question

I want to use indexOf() on an array of objects. For example:

var arr;
var arr[0] = {a: 1, b: 2};
var arr[1] = {a: 1, b: 3};
var obj = {a: 1, b: 2};

console.log(arr.indexOf(obj));

This will print -1 because arr[0] does not equal obj. How can I make this work (ie, print 0)?

Answer 1

You would have to compare the properties. Something like this would work:

 var arr = []; arr[0] = {a: 1, b: 2}; arr[1] = {a: 1, b: 3}; console.log(arr.findIndex(o => oa === 1 && ob === 2)); //0 console.log(arr.findIndex(o => oa === 1 && ob === 3)); //1 

Answer 2

The array.findIndex() function will bring back the index for the first value that the comparing function results are true . I have a function that I use to compare if two objects are equal that can be used in this example.

 var obj = {a: 1, b: 2}; var arr = []; arr[0] = {a: 1, b: 2}; arr[1] = {a: 1, b: 3}; var idx = arr.findIndex(element => areObjsEqual(element,obj)); console.log(`The index is: ${idx}`); //Function to check if two js objects are equal function areObjsEqual(a, b) { // Create arrays of property names var aProps = Object.getOwnPropertyNames(a); var bProps = Object.getOwnPropertyNames(b); // If number of properties is different, // objects are not equivalent if (aProps.length != bProps.length) { return false;} //loop through the object and compare the property values for (var i = 0; i < aProps.length; i++) { var propName = aProps[i]; // If values of same property are not equal, // objects are not equivalent if (a[propName] !== b[propName]) { return false; } } // If we made it this far, objects // are considered equivalent return true; } 

Answer 3

I created a similar function which compares almost anything, a while back:

 function similar(needle, haystack, exact){ if(needle === haystack){ return true; } if(needle instanceof Date && haystack instanceof Date){ return needle.getTime() === haystack.getTime(); } if(!needle || !haystack || (typeof needle !== 'object' && typeof haystack !== 'object')){ return needle === haystack; } if(needle === null || needle === undefined || haystack === null || haystack === undefined || needle.prototype !== haystack.prototype){ return false; } var keys = Object.keys(needle); if(exact && keys.length !== Object.keys(haystack).length){ return false; } return keys.every(function(k){ return similar(needle[k], haystack[k]); }); } var obj1 = {a:1, b:[5, 'word'], c:{another:'cool', neat:'not', num:1}, d:'simple string'}; var obj2 = {a:1, b:[5, 'word'], c:{another:'cool', neat:'not', num:1}, d:'simple string'}; console.log(similar(obj1, obj2, true)); // true for exact match obj2.newProp = 'new value'; // extra haystack prop added console.log(similar(obj1, obj2, true)); // true for exact - result is false here console.log(similar(obj1, obj2)); // not exact - obj1 properties and values are in obj2 

Of course similar can be made to find the similarIndex of a needle (anything) in an haystack (array of anything) , like so:

 function similar(needle, haystack, exact){ if(needle === haystack){ return true; } if(needle instanceof Date && haystack instanceof Date){ return needle.getTime() === haystack.getTime(); } if(!needle || !haystack || (typeof needle !== 'object' && typeof haystack !== 'object')){ return needle === haystack; } if(needle === null || needle === undefined || haystack === null || haystack === undefined || needle.prototype !== haystack.prototype){ return false; } var keys = Object.keys(needle); if(exact && keys.length !== Object.keys(haystack).length){ return false; } return keys.every(function(k){ return similar(needle[k], haystack[k]); }); } function similarIndex(needle, haystack, exact){ for(var i=0,l=haystack.length; i<l; i++){ if(similar(needle, haystack[i], exact)){ return i; } } return -1; } var objArray = [{a:1, b:[5, 'wtf'], c:{another:'cool', neat:'not', num:1}, d:'simple string'}, {a:1, b:[5, 'word'], c:{another:'cool', neat:'not', num:1}, d:'simple string'}, {a:1, b:[5, 'word'], c:{another:'cool', neat:'not', num:4}, d:'simple string'}]; var testObj = {a:1, b:[5, 'word'], c:{another:'cool', neat:'not', num:1}, d:'simple string'}; console.log(similarIndex(testObj, objArray, true)); // exact - index is 1 in this case objArray[1].newProp = 'new value'; // haystack array element 1 gets new property and value console.log(similarIndex(testObj, objArray, true)); // exact - -1 result here console.log(similarIndex(testObj, objArray)); // not exact - index 1