短的例子:

if (typeof(arr[key]) === "undefined") {
  arr.push(key);
}

你可以用一个自定义方法扩展Array原型:

// check if an element exists in array using a comparer function
// comparer : function(currentElement)
Array.prototype.inArray = function(comparer) { 
    for(var i=0; i < this.length; i++) { 
        if(comparer(this[i])) return true; 
    }
    return false; 
}; 

// adds an element to the array if it does not already exist using a comparer 
// function
Array.prototype.pushIfNotExist = function(element, comparer) { 
    if (!this.inArray(comparer)) {
        this.push(element);
    }
}; 

var array = [{ name: "tom", text: "tasty" }];
var element = { name: "tom", text: "tasty" };
array.pushIfNotExist(element, function(e) { 
    return e.name === element.name && e.text === element.text; 
});

像这样的吗?

var item = "Hello World";
var array = [];
if (array.indexOf(item) === -1) array.push(item);

与对象

var item = {name: "tom", text: "tasty"}
var array = [{}]
if (!array.find(o => o.name === 'tom' && o.text === 'tasty'))
    array.push(item)

这里你有一种方法可以在一行中为两个数组做这件事:

const startArray = [1,2,3,4]
const newArray = [4,5,6]

const result = [...startArray, ...newArray.filter(a => !startArray.includes(a))]

console.log(result);
//Result: [1,2,3,4,5,6]

如果你的项目包含lodash，使用unionBy方法会很简单

import {unionBy} from "lodash";

let arrayObj = [
    { name: "jhon", text: "guitar"},
    { name: "paul", text: "bass" },
    { name: "george", text: "guitar" }
];

// this object will be added to the array
arrayObj = unionBy(arrayObj, [{name: 'ringo', text: 'drums'}], 'name')

// this object will be ignored because already exists  
arrayObj = unionBy(arrayObj, [{name: "jhon", text: "guitar"}], 'name')

我更喜欢使用原生js Array.prototype.some()，即使在jqenv中 文档:w3s some or mdn some

let arr = [
    { name: "tom", text: "tasty" },
    { name: "tom", text: "tasty" }
];
let oneMore = { name: "tom", text: "tasty" };
!arr.some(i => i.name == oneMore.name && i.text == oneMore.text)
  && arr.push(oneMore);