javascript，如何理解数组遍历相关的find/filter/map函数？

var data = [
    { id: 0, name: "苏南" },
    { id: 1, name: "sunan大叔" },
    { id: 2, name: "苏南大叔" },
];

var result0 = data.find(item => item.id >= 1);
var result1 = data.find(item => {
    return item.id >= 1
});
console.log(result0, result1);                 // { id: 1, name: 'sunan大叔' } 
var result2 = data.find(item => item.id >= 10);
console.log(result2);                          // undefined

var result3 = data.filter(item => item.id !== 1);
var result4 = data.filter(item => {
    return item.id !== 1;
});
console.log(result3, result4);         // [ { id: 0, name: '苏南' }, { id: 2, name: '苏南大叔' } ]
var result5 = data.filter(item => item.id >= 10);
console.log(result5);                  // []

var data = [
    { id: 0, name: "苏南" },
    { id: 1, name: "sunan大叔" },
    { id: 2, name: "苏南大叔" },
];
var result6 = data.map(item => item.id === 1 ? "等于1" : "不等于1");
var result7 = data.map(item => {
    return item.id === 1 ? "等于1" : "不等于1";
});
console.log(result6, result7);
// [ '不等于1', '等于1', '不等于1' ] [ '不等于1', '等于1', '不等于1' ]
var result8 = [].map(item => {
    return item.id === 1 ? "等于1" : "不等于1";
});
console.log(result8);    // []

let arr = [0, 1, 2, 3]
arr.reduce(function (previousValue, currentValue) {
    console.log(currentValue);
},arr[0]);